modify launch controllers

[gar1948]

My son purchased the Estes Thunderstar which has a two engine cluster. I have only launched single engine models in the past. What is the proper way to launch this? I have the Estes electron beam controller. coming back to hobby after 30 years. Thanks--- :)

[Old Rocketeer "II"]

You'll have 100% success if you use the new Quest Q2G2 igniters along with the Quest 9V Launch controller. These are the best cluster igniters ever !!! Throw the old Aunt Ester controller away...

http://www.questaerospace.com/Itemdesc.asp?ic=7024&eq=&Tp=

[luke strawwalker]

Yeah, I totally agree with OR II here... and not because I own the company LOL:)

The Q2G2's are as far ahead of the Estes Solar Ignitors as they were beyond bare nichrome wire back in the day-- the best thing to come along in LPR rocket ignitors in probably 30 years! VERY good product!

The Quest controller is nice too, nicer than the old Estes cheapy controllers, that's for sure. I'm not crazy about buzzers; I prefer LED lights actually, and have two rewired older Estes controllers wired for use with an external battery (battery charger-style clips for car batteries or the best thing since sliced bread-- a car battery 'booster pack' emergency jumper box!) with an LED for battery connection continuity (runs all the time the battery is connected) and another different color LED for the ignitor continuity. Such LED indicators, with built in resistors are available at Radio Shack and fairly easy to install. For a quick switchout that will work with Q2G2's, you can swap in a resistor-equipped LED flashlight bulb replacement into the Estes controller-- it should choke the current draw down enough so that the ignitor won't go off when you insert the key, which Q2G2's will do with a standard Estes controller with the stupid flashlight bulbs, because they pass too much current on to the ignitor.

Hope this helps! OL JR :)

[GregGleason]

Throw the old Aunt Ester controller away...

http://www.questaerospace.com/Itemdesc.asp?ic=7024&eq=&Tp=

But wait! If you act now, we will throw in a Slap-Chop! :D

Greg

[garmtn]

Hi, W/the quest igniters u can probably get away w/twisting the 2 leads from each motor together. Otherwise make yourself a "clip whip." Just get some 14 guage lamp cord and aligator clips. Soldering is always best. Make yourself two, " 2 leads into one lead." Just remember to hook up one lead from each engine to a "cw." TTY Glenn NAR 89197 :D

[gar1948]

Thanks for all your responses.
Sorry but what is a "cw" ? Will this work on the Estes electron beam controller I have? I assume with the two leads into one you mean cut the alligator clip off each lead and attach two wires with a clip on each? Will there be enough juice to ignite both engines? Thanks

[GregGleason]

Thanks for all your responses.
Sorry but what is a "cw" ? W

CW = Clip Whip

See link (http://www.sunward1.com/cluster-cables.htm) for examples.

Greg

[luke strawwalker]

Thanks for all your responses.
Sorry but what is a "cw" ? Will this work on the Estes electron beam controller I have? I assume with the two leads into one you mean cut the alligator clip off each lead and attach two wires with a clip on each? Will there be enough juice to ignite both engines? Thanks

The easiest way to make clip whips is to get a roll of fairly cheap but fairly thick (at LEAST 16 guage) automotive wire... you can get a roll of this at the dollar store for like, oh, a dollar. This the multistrand wire typically used in automotive wiring. Stop by Radio Shack, and back in the drawers of electronic parts you can get a pack of copper-clad microclips fairly cheap (few bucks). If you don't have a soldering iron and solder, you can get that at Walmart fairly cheap too (about 10 bucks for an iron and a couple bucks for a roll of electrical rosin core solder.)

Cut four pieces of wire about 4 inches long. Strip the insulation off both ends about 1/2 inch back from the end. Twist two ends together and solder them together side by side-- this is where you'll clip your existing launch clips onto the whip from your existing launcher. Take a microclip and attach it to the free end of each wire (one clip per wire). Stick the wire through the little hole in the back of the microclip and fold it over. Touch it to the soldering iron to heat it a second, and apply the solder to it til it melts a small drop of solder into the clip and wire to solder them together. Don't get the clip too hot or the solder will be drawn up into the pivot pin between the two halves of the clip and weld them solid (don't ask me how I know this :D ) If that happens cut the clip off, restrip the wire, and start again. You should now have two clips attached to two pieces of wire that are soldered together on the other end.

To use them, attach the one of the two clips to one side of each of the two ignitors on your rocket, and then attach one of the two clips from the launcher leads onto the end where the wires are soldered together... do the same for the other side. Launch as normal.

Or you could just twist the ends of two Quest ignitors together and clip your existing launcher clips on each pair...

DO NOT twist two of the ingitor leads together and then attach the regular launcher clips onto the two remaining ignitor 'free' ends... this will form a SERIES circuit, and when the first ignitor burns through it will kill the power to the other ignitor, preventing it from firing... ALWAYS use PARALLEL circuits for ignitors, so one lead from EACH IGNITOR is attached to one lead from the launcher and the other lead of EACH IGNITOR is attached to the other lead from the launcher... the clip whip just allows you to accomplish this... :)

Good luck! OL JR :)

[garmtn]

I did use general term in my message. A"CW" is short for a clip-whip. TTY Glenn ;)

[gar1948]

Thank you for easy to understand instructions. I really appreciated everyone responding to my pretty basic questions. You guys are very understanding of beginners. Not all sites are like that for any hobby. :chuckle:

[luke strawwalker]

Thanks for all your responses.
Sorry but what is a "cw" ? Will this work on the Estes electron beam controller I have? I assume with the two leads into one you mean cut the alligator clip off each lead and attach two wires with a clip on each? Will there be enough juice to ignite both engines? Thanks

The regular Electron Beam controller is kinda iffy for lighting a cluster. Supposedly the Estes "E" controller has a little more power and slightly thicker wire leads (hence less resistance) which makes it better for lighting clusters. Personally I think the main limitation is the 6 volt power supply (4 AA batteries) and the fact that the AA batteries don't have much current capacity. For launching this one cluster rocket, I'd say it'd probably be ok, but IF you get everything just right (with the ignitors) and have fresh hot batteries in the controller. I'd put the odds at about 60% or so getting both motors to ignite promptly. The "E" controller is a little better, but the leads are still thinner than they should be (I prefer at least 'lamp cord' thickness-- in fact I buy packs of lamp cord from the dollar store for working on controllers and stuff) plus, it's STILL only a 6 volt system. The more voltage, the more current you're going to push through the ignitors, and it's the current that heats the ignitors up and causes them to light the pyrogen. Hence, higher voltage, more current, the faster and more reliably they light, especially in clusters where they've got to light as soon as possible TOGETHER.

The Quest controller IMHO is a MUCH better solution to this problem-- it runs off a 9 volt battery which automatically means it's going to send more current through the ignitor, and it can also be used with 'outside power sources' using their clips. This would be a much better choice for two engine clusters than the standard Estes controllers.

The most important thing I could suggest is using the Quest Q2G2 ignitors-- they are built more like HPR ignitors than the standard Estes type LPR ignitors (Solar Ignitors) and are more robust, but more importantly they have a MUCH MUCH lower firing current requirement than the standard Estes ignitors. In fact, an Estes controller will likely fire them when you insert the safety key because the light bulb passes too much current. You can remedy this by replacing the stock flashlight bulb in the Estes controller with an LED flashlight bulb with built-in resistor-- this will choke down the current passed through the ignitors by the continuity bulb enough so they don't fire (test this with an ignitor outside the motor first though) Using these ignitors with an LED bulb equipped Estes stock controller, I'd put your chances of a successful firing of both ignitors at better than 90%. With the Quest controller I'd say more like 95%+.

If you're JUST going to be launching this ONE cluster rocket, then that's probably the way to go-- Walmart sells the LED light bulbs back in the camping department fairly cheap, and it should just insert into the controller where the existing bulb goes. If you want to upgrade your controllers, like I did, you can replace the existing flashlight bulbs with LED indicators from Radio Shack, wire it for external battery hookup and use a car battery jumper pack with it's 12V sealed gel-cell hi-amperage battery for a power source (could light probably 100 Estes ignitors at once if the connecting wiring is heavy enough!) and rewire it with heavier guage lamp cord. I even equipped mine with "lamp cord plugs" between the microclips and the controller, so I can use a standard extension cord for launch leads-- no more tangled doorbell wires running out to the pad. Plus, when I'm done, I can unplug the extension cord and use it for other stuff, and plug the ignitor clips on their foot long cord into the foot long cord plug coming out of the controller, and roll the wires up tight around th controller and store it in the range box tight and neat. Very handy.

If you want more info on converting your controllers, lemme know. I've done a couple of them and they work great!

Later! OL JR :)

[gar1948]

Hi luke strawwalker---
Thanks for the info. This may be a one time 2 engine cluster launch. I have several 7.2 volt r/c battery packs. Will that give me enough juice for the job? Do you have detail plans for using outside battery source with the estes controller. Can I replace the power cord on the controller with heavier lampshade cord, use the outside battery and leave the stock bulb or do I have to change it?
Thanks for all your time .

[garmtn]

Up until a week ago, I had to remove my 12 v tractor battery from tractor. Now I acquired a 12 v car battery. FYI: I agree with responses u have gotten. U need "lamp cord" and a lot of juice for clusters. A 6to 9 v system is fine for single rocket motors, even if slow. Also, my tractor battery was too weak to start the machine so had to recharge. Launching really drains it. TTY Glenn :cool:

[luke strawwalker]

Hey gar...

The 7.2 packs should work pretty well-- the R/C packs tend to have pretty high C-ratings, which means they can deliver a pretty good amount of current on short notice. 7.2 volts is a little lower voltage than ideal (12 is better) You COULD wire the two 7.2 packs in series to get 14.4 volts, which would be plenty. Requires a jumper wire between packs (positive of one pack to negative of the other, with the remaining terminal on each pack connected to the launcher.) You can probably do this using spade terminals and rubber band the pack together, and make a jumper wire out of automotive wire with a spade terminal crimped on each end.

Here's a couple pics of what I'm using-- I reworked my 20 year old Estes "Electron Beam" controller for external battery use using lamp cord and a pair of battery charger clamps I picked up for a few bucks at the auto supply. Works great. You can see the jumper pack that I use for power. It's not only VERY handy and portable for launches, can be recharged in the house or in the vehicle while driving, but it does double-duty as a handy jumper for getting tractors started when the batteries have been sitting awhile (I'm a farmboy too running cattle on two farms 100 miles apart, so I know ALL about that kind of stuff :) ) I really don't know how I got along without the thing for so long...

The Electron Beam controller was rewired inside I simply unscrewed the back of the controller (I think the newer ones are glued or 'snap' together, so they'll require more work and glue or screws to put it back together most likely) and once inside, I found the terminals where the AA batteries connected to the brass contacts inside going to the flashlight bulb and launch button, and simply connected the two wires using ring connectors I soldered on for the best connection-- but a simple crimp fitting is probably okay too. Be sure you tie a simple knot in the wire where it comes out of the case for strain relief so you don't inadvertantly pull the wires out of the controller accidentally. I carved a little notch in the opposite end of the controller from the launch leads with the knot just inside the case halves. I removed the old flashlight bulb and threw it away (I NEVER liked the stupid things-- half the time I'd hook up the ignitor insert the key and nothing-- no light from the bulb, and I'd go to the pad and wiggle and work and clean the clips and test with the key again, nothing, finally wiggle the stupid flashlight bulb and it would turn out IT was the one with bad contact, not the clips) Replacing those stupid bulbs eliminates this problem and reduces the current substantially during continuity checks, reducing power drain from the battery, and more importantly, reducing the current passing through the ignitor for continuity checks enough that it SHOULD be safe for even sensitive ignitors. (Bench test it with an ignitor first-no motor!) Now you CAN just install a flashlight LED replacment bulb into your controller from the camping department at Walmart, and probably achieve much the same thing as I did. I left the empty socket though and installed a pair of LED indicators from Radio Shack. They're in the electronic parts dept in little baggies. They are little button lenses about 1/4 inch in diameter, with a small body about an inch or so long on the back, with a threaded nut to hold them in the hole that you drill in the controller. These indicators have the advantage that they already have the resistors wired inside the indicator between the power lead and the LED, choking down the current passing through the semiconductor bridge of the LED to prevent it from burning out. This also limits the current going to the ignitor. Notice in the pics, one LED is RED and one is AMBER.... The RED LED is simply wired directly to the two power leads coming in from the battery so I know if I have a good connection to my power source (and if using a golf cart battery or club battery I know if it's dead or not, clip jumped off, etc.) This is handy because I switched over to car battery clips 20 years ago and found that sometimes when the light bulb didn't come on, it wasn't the bulb, it was the battery clips didn't have good contact with the car battery. The RED LED is connected to the same two screws that hold the ring connectors going out to the battery, with another pair of ring connectors soldered or crimped onto the ends of the LED indicator lead wires. (Be sure you connect them up with the right polarity or the LED WON'T light up--LED's only pass current in ONE direction, and if it doesn't light up, simply reverse the wires) The AMBER LED is the continuity indicator-- it replaces the dinky lightbulb. It is wired up with ring terminals on the LED leads under the screws holding the two brass contacts inside the controller between the contacts of the light bulb. There will be a brass contact with a hole with two notches at the top of the light bulb socket, and another brass contact below the light bulb which presses on the little contact on the bottom of the bulb, the LED connects to these strips with ring connectors at the nearest screw holding the clips in the case. I also replaced the steel launch keys, since they tend to rust and lose contact and don't conduct very well, with copper launch keys made from regular 14-16 guage romex house wire. You can get a scrap of this from the lumberyard or an electrician for free, remove the bare ground wire (or if it's smaller, pull one of the white or black insulated wires out of the jacketing and then strip all the insulation off it with a knife, bend it as straight as you can get it, cut off a piece a couple inches long or so, and bend one end around into a loop for a 'handle' with pliers. If you want to get fancy you can solder the loop closed like I did, since copper is a little soft and bends fairly easily compared to steel. These keys don't corrode like steel and conduct probably at least ten times better than steel keys. I also removed the existing light-grade bell wire that Estes equipped the controller with and replaced it with lamp cord, again tying a knot for strain relief inside the case, and connect it up with ring connectors or crimps in exactly the same place as the existing dinky bell wire is connected. I enlarged the wire hole in the front of the case, and installed a cheapy "replacement lamp plug" on the end of the cord so I can use a regular extension cord for launcher leads. Use a female plug on the launcher, and then use a male plug and a piece of lamp cord wired into the plug, and then solder brass clips from radio shack on the other end of the lamp cord after seperating the leads about a foot or so back. To seperate lamp cord into seperate leads, just make a small cut through the very end of the wire between the two wires in the little notch between them, then pull them apart-- they'll "unzip" as you pull. Just plug your extension cord male end into the controller plug and the clip end male plug into the other end of the extension cord after pulling it out to the launch pad.

The second launcher is an old Estes POLA-PULSE controller, the kind Estes sold 20 years ago that used the Polaroid flat 3x3 inch square camera batteries. Those weren't around long and were pretty expensive and ill suited to launcher duty, so the first thing I did was swap in a lampcord lead (as with the other controller I did later) to replace the internal battery with clips to connect to the car battery. I hated the bulb on there as well, so I gutted an old VCR I had laying around for LED's and resistors, soldered the resistors directly to the LED legs, and soldered small extension wires (actually the old ignitor lead wires from the thin leads that come with the launcher which is too small (too much resistance which limits current to the ignitors, part of the reason why you can count to zero and hit "launch" and hold the button down on an Estes controller and usually the rocket doesn't launch for at least another half-second or second or so.) The stupid bell wire is just too small for reliable operation, but Estes likes it because it's cheap. If you want a good controller though, this is the first thing that has to go. All I had was two green LED's but that's ok, because I wired one up to directly replace the light bulb using short lengths of wire to connect the LED's to the brass contacts inside the case with ring terminals, and the other green LED is connected up directly across the two external battery wires coming in from the battery charger clips that connect the controller to the car battery. Again be sure to connect the LED's up with the proper polarity or they WON'T light up. Be sure you connect the battery clips correctly too (red to positive, black to negative) or they LED's won't light. The bulbs work either direction, but LED's can only flow in ONE direction. It's not a big deal though once you wire it up. I made another copper key for this controller as well. I used the sharp tip of a test light to carefully scribe the case to tell me what each LED means (just for reference, it's basically intuitive, but it helps when someone else launches for me when I'm taking photos so they know what the LED's do) and then painted a bit of liquid paper into the scribe marks to highlight the letters for easy visibility. The launcher leads are again done away with the dinky bell wire and replaced with lamp cord and plugs for use with an extension cord.

I don't have any wiring diagrams but I could whip some up if you really need them.

Later! OL JR :)

[tfischer]

Just a nitpick but that's actually an old "Solar" launch controller. I still have mine too and use it as a backup :)

http://plans.rocketshoppe.com/pubs/Estes/solar_launch.pdf

[BEC]

Beat me to it. I don't think I'll be hacking my Solar controller either... but LED indication and better wiring mods to Electron beams - yes. And I might put one of those LED "bulbs" in the Solar controller.

While I haven't done it yet, I'd expect an Electron Beam to have no problem with a two-engine cluster with paralleled Quest Q2G2 igniters though fresh cells would be good.

I've done at least 50 launches now on my modified Electron Beam with a big LED from Radio Shack as the continuity indicator on the same set of Costco AAs and it's still firing Estes igniters quickly. After verifying continuity I only hold the key down for the last second or two of the countdown. That and the low drain of the LED probably help.

I have to quibble with one comment in this thread: higher voltage is better for faster ignitions, but a tiny 9V battery as used in the Quest controller is not all that great at delivering current. I haven't done the tests, but I wouldn't be surprised to see the 4 AA alkalines in an Electron Beam being able to deliver more current into a given igniter than the tiny 9V battery in a Quest controller. Of course Quest igniters need so little current that that's not an issue for normal single-engine use.

A 7.2V sub-C NiCd pack from an RC car or airplane on the other hand could deliver many tens of amps for a short time if asked. When I get far enough in my BAR-dom to get back to clusters, that's probably where I'll go for portable reliable power.

Added later: I thought of a way to verify my thoughts about 4 AAs vs. an alkaline 9V "tranisistor radio" battery. I have a data logger that's designed for RC electric power systems (airplanes, cars). It's capable of handling 100A. That is more than anything we've discussed in this thread save for perhaps a really good NiCd pack (or a car battery) can dump. I'll try to create and post graphs of volts and amps with an Electron Beam and a Quest controller essentially using the logger - or a dead short across the logger - as the igniter this evening. I have enough surplus Estes igniters I could probably test those as the load as well. I've no Q2G2s to waste.....

[luke strawwalker]

Just a nitpick but that's actually an old "Solar" launch controller. I still have mine too and use it as a backup :)

http://plans.rocketshoppe.com/pubs/Estes/solar_launch.pdf


Quite right, thanks... Been quite a few late nights around here recently-- my wife had her tonsils out and I have to get up and measure out her medicine-- she doesn't trust herself to measure out two TEASPOONS of the Tylenol/Codiene instead of two TABLESPOONS when she's fuzzy-headed...

I laughingly told her two tablespoons would give her a LONG and interesting trip though... :)

Later! OL JR :)

[luke strawwalker]

Beat me to it. I don't think I'll be hacking my Solar controller either... but LED indication and better wiring mods to Electron beams - yes. And I might put one of those LED "bulbs" in the Solar controller.

While I haven't done it yet, I'd expect an Electron Beam to have no problem with a two-engine cluster with paralleled Quest Q2G2 igniters though fresh cells would be good.

I've done at least 50 launches now on my modified Electron Beam with a big LED from Radio Shack as the continuity indicator on the same set of Costco AAs and it's still firing Estes igniters quickly. After verifying continuity I only hold the key down for the last second or two of the countdown. That and the low drain of the LED probably help.

I have to quibble with one comment in this thread: higher voltage is better for faster ignitions, but a tiny 9V battery as used in the Quest controller is not all that great at delivering current. I haven't done the tests, but I wouldn't be surprised to see the 4 AA alkalines in an Electron Beam being able to deliver more current into a given igniter than the tiny 9V battery in a Quest controller. Of course Quest igniters need so little current that that's not an issue for normal single-engine use.

A 7.2V sub-C NiCd pack from an RC car or airplane on the other hand could deliver many tens of amps for a short time if asked. When I get far enough in my BAR-dom to get back to clusters, that's probably where I'll go for portable reliable power.

Added later: I thought of a way to verify my thoughts about 4 AAs vs. an alkaline 9V "tranisistor radio" battery. I have a data logger that's designed for RC electric power systems (airplanes, cars). It's capable of handling 100A. That is more than anything we've discussed in this thread save for perhaps a really good NiCd pack (or a car battery) can dump. I'll try to create and post graphs of volts and amps with an Electron Beam and a Quest controller essentially using the logger - or a dead short across the logger - as the igniter this evening. I have enough surplus Estes igniters I could probably test those as the load as well. I've no Q2G2s to waste.....

Yes, you're probably right. 9 volts is capable of DRIVING more current through the ignitor (like more pressure from a garden hose) but if the source (9 volt can battery, which incidentally consists of 6 AAAA 'baby cells' inside) is only capable of delivering "X" number of amps at dead short (due to capacity and battery internal resistance) then yes, if the 6 volt AA stack has lower internal resistance and more capacity I'm sure it could deliver more amperage. I guess I shoulda clarified my remarks a bit more... I had to shorten that post up three times before it'd go anyway... LOL:)

Oh well, sounds like yall have things well in hand... :) OL JR :)

[tfischer]

Can you describe (or point me to a thread) how to wire in an LED into a 6V (or 12V) circuit? I do mean a standard LED, not one of the 6V LED bulbs also mentioned.

Thanks,
-Tim

[luke strawwalker]

Can you describe (or point me to a thread) how to wire in an LED into a 6V (or 12V) circuit? I do mean a standard LED, not one of the 6V LED bulbs also mentioned.

Thanks,
-Tim

Hey Tim... the voltage doesn't really matter much with the LED's I've used, so there isn't really any difference between a 6 volt and 12 volt system, etc. The main thing is, if using a plain LED resistor in a housing or gluing it directly into a hole in the controller, you MUST use a resistor in series with the LED to keep the current down so it doesn't burn out the LED's semiconductor bridge. The LED itself has VERY little resistance and hence too much current will flow through it unless there's a resistor there to restrict the current flow. IF you use LED INDICATORS from Radio Shack (part # 276-272 Amber or 276-270 Red) they are already equipped with the proper resistor inside the LED housing, so it's a "plug and play" replacment.

Anyway, here's a couple diagrams I whipped up and scanned in. Any questions feel free to ask.

Hope this helps! OL JR :)

[tfischer]

Thanks!

[BEC]

OK - here are the actual test results.... they surprise me a little....

I tried three controllers: The Electron Beam I modded for LED continuity indication and which has fired at least 50 rockets on the current set of Costco AA cells, an unmodified Electron Beam that has fired maybe one or two (it also has Costco AA alkalines in it) and a Quest 9V controller which has also fired only a handful of rockets (and all but one of those on Quest igniters) on its Duracell 9V.

The surprise, as you'll see in the graph, is that their initial current into a dead short is very close to the same - about 4.5A - but as you'd expect from the tiny battery involved, the Quest controller's current falls much more quickly.

The bump in the green trace (stock Electron Beam) at about 4s is when the key was held down. The other two's continuity indication currents are barely visible at that scale.

The open circuit voltage of the Quest controller (key in, fire button down) is about 8.9V. The other two are 6.0 and 6.2.

All are stock wiring, stock clips (though I cleaned the well-used clips with an emery board first).

From this, and without testing actual igniters, I'd think either the Estes or the Quest controller could fire a two-engine cluster using Q2G2s....but since the Estes with the incandescent lamp draws 170 mA with the safety key in you gotta have the LED mod or a Quest controller (20-30 mA) as has been discussed before in the Quest igniter thread.

The data were taken with the clips of the controller clipped on the input of my Medusa Research Power Analyzer Pro and the output either shorted (for the current graph) or open circuit (voltage readings).

[Jeff Walther]

Can you describe (or point me to a thread) how to wire in an LED into a 6V (or 12V) circuit? I do mean a standard LED, not one of the 6V LED bulbs also mentioned.

For the actual wiring, just put the appropriate resistor in series with the LED, and get the polarity of the LED correct with respect to your battery. So, verbally, positive battery terminal to resistor lead, other resistor lead to anode of diode (side without stripe, or with + symbol), cathode of diode (side with stripe or - symbol) to negative battery terminal. The resistor can actually go on either side of the diode.

All About Circuits: Diodes (http://www.allaboutcircuits.com/vol_3/chpt_3/1.html)

I thought I'd babble a bit about picking the resistor value. It isn't terribly critical...

The diode has two characteristics which are useful to know. The first if the forward voltage, Vf, and the second is the maximum current it is rated for.

When the LED is lit, it conducts much like a piece of wire, except that it will cause a fixed voltage drop (doesn't depend on current (much)) of Vf.

The maximum current is the amount you don't want to exceed through the diode.

A regular diode typically has a Vf of .7V, but it looks like LEDs are more commonly at 1.5V and up.

For indicator LEDs you usually want to shoot for about 20 mA (milli amperes, thousandths of an amp) for the maximum current.

Ohms law states that V = I*R. Or voltage equals current times resistance.

So our V here is + the battery voltage, but minus the Vf of the diode. So, if you have a 6V battery and a 1.5 Vf LED, your V in this case is 4.5V. The I is our target of 20 mA. We want to find the R or resistance.

So R = V/I = 4.5/.020 = 225 ohms.

If you put a 12V battery in the same controller, you'll get (12 - 1.5) / 225 = 47 mA of current through the diode and the igniters.

So knowing those simple things you can pick a resistor to target the current you want in standby mode, for a given LED.

See also:

All about Circuits: Diode Ratings (http://www.allaboutcircuits.com/vol_3/chpt_3/3.html)

[Jeff Walther]

Oh, I stopped too soon. This link (scroll down to the LED section) covers what I just discussed with circuit diagrams and pictures and more examples:

All About Circuits: Special Purpose Diodes (http://www.allaboutcircuits.com/vol_3/chpt_3/12.html)

[BEC]

A regular diode typically has a Vf of .7V, but it looks like LEDs are more commonly at 1.5V and up.

For indicator LEDs you usually want to shoot for about 20 mA (milli amperes, thousandths of an amp) for the maximum current.


I found in shopping for LEDs to do this sort of conversion that the forward voltage varies a great deal depending on LED color and also how bright it is. A 1.5Vf rating is pretty low - I've seen them up to well over double that. The current rating it has also varies quite a bit.

So it's somewhat important to do the resistor calculation for the particular LED you've selected as well as the voltage (or range of voltages) you expect to supply to it in the launch controller.

[GregGleason]

I thought I'd babble a bit about picking the resistor value. It isn't terribly critical...


I appreciate the "babble", Jeff. The electrical side of rocketry is still somewhat of a struggle for me to understand, so it is helpful.

Greg

[gar1948]

Hey gar...

The 7.2 packs should work pretty well-- the R/C packs tend to have pretty high C-ratings, which means they can deliver a pretty good amount of current on short notice. 7.2 volts is a little lower voltage than ideal (12 is better) You COULD wire the two 7.2 packs in series to get 14.4 volts, which would be plenty. Requires a jumper wire between packs (positive of one pack to negative of the other, with the remaining terminal on each pack connected to the launcher.) You can probably do this using spade terminals and rubber band the pack together, and make a jumper wire out of automotive wire with a spade terminal crimped on each end.

Here's a couple pics of what I'm using-- I reworked my 20 year old Estes "Electron Beam" controller for external battery use using lamp cord and a pair of battery charger clamps I picked up for a few bucks at the auto supply. Works great. You can see the jumper pack that I use for power. It's not only VERY handy and portable for launches, can be recharged in the house or in the vehicle while driving, but it does double-duty as a handy jumper for getting tractors started when the batteries have been sitting awhile (I'm a farmboy too running cattle on two farms 100 miles apart, so I know ALL about that kind of stuff :) ) I really don't know how I got along without the thing for so long...

The Electron Beam controller was rewired inside I simply unscrewed the back of the controller (I think the newer ones are glued or 'snap' together, so they'll require more work and glue or screws to put it back together most likely) and once inside, I found the terminals where the AA batteries connected to the brass contacts inside going to the flashlight bulb and launch button, and simply connected the two wires using ring connectors I soldered on for the best connection-- but a simple crimp fitting is probably okay too. Be sure you tie a simple knot in the wire where it comes out of the case for strain relief so you don't inadvertantly pull the wires out of the controller accidentally. I carved a little notch in the opposite end of the controller from the launch leads with the knot just inside the case halves. I removed the old flashlight bulb and threw it away (I NEVER liked the stupid things-- half the time I'd hook up the ignitor insert the key and nothing-- no light from the bulb, and I'd go to the pad and wiggle and work and clean the clips and test with the key again, nothing, finally wiggle the stupid flashlight bulb and it would turn out IT was the one with bad contact, not the clips) Replacing those stupid bulbs eliminates this problem and reduces the current substantially during continuity checks, reducing power drain from the battery, and more importantly, reducing the current passing through the ignitor for continuity checks enough that it SHOULD be safe for even sensitive ignitors. (Bench test it with an ignitor first-no motor!) Now you CAN just install a flashlight LED replacment bulb into your controller from the camping department at Walmart, and probably achieve much the same thing as I did. I left the empty socket though and installed a pair of LED indicators from Radio Shack. They're in the electronic parts dept in little baggies. They are little button lenses about 1/4 inch in diameter, with a small body about an inch or so long on the back, with a threaded nut to hold them in the hole that you drill in the controller. These indicators have the advantage that they already have the resistors wired inside the indicator between the power lead and the LED, choking down the current passing through the semiconductor bridge of the LED to prevent it from burning out. This also limits the current going to the ignitor. Notice in the pics, one LED is RED and one is AMBER.... The RED LED is simply wired directly to the two power leads coming in from the battery so I know if I have a good connection to my power source (and if using a golf cart battery or club battery I know if it's dead or not, clip jumped off, etc.) This is handy because I switched over to car battery clips 20 years ago and found that sometimes when the light bulb didn't come on, it wasn't the bulb, it was the battery clips didn't have good contact with the car battery. The RED LED is connected to the same two screws that hold the ring connectors going out to the battery, with another pair of ring connectors soldered or crimped onto the ends of the LED indicator lead wires. (Be sure you connect them up with the right polarity or the LED WON'T light up--LED's only pass current in ONE direction, and if it doesn't light up, simply reverse the wires) The AMBER LED is the continuity indicator-- it replaces the dinky lightbulb. It is wired up with ring terminals on the LED leads under the screws holding the two brass contacts inside the controller between the contacts of the light bulb. There will be a brass contact with a hole with two notches at the top of the light bulb socket, and another brass contact below the light bulb which presses on the little contact on the bottom of the bulb, the LED connects to these strips with ring connectors at the nearest screw holding the clips in the case. I also replaced the steel launch keys, since they tend to rust and lose contact and don't conduct very well, with copper launch keys made from regular 14-16 guage romex house wire. You can get a scrap of this from the lumberyard or an electrician for free, remove the bare ground wire (or if it's smaller, pull one of the white or black insulated wires out of the jacketing and then strip all the insulation off it with a knife, bend it as straight as you can get it, cut off a piece a couple inches long or so, and bend one end around into a loop for a 'handle' with pliers. If you want to get fancy you can solder the loop closed like I did, since copper is a little soft and bends fairly easily compared to steel. These keys don't corrode like steel and conduct probably at least ten times better than steel keys. I also removed the existing light-grade bell wire that Estes equipped the controller with and replaced it with lamp cord, again tying a knot for strain relief inside the case, and connect it up with ring connectors or crimps in exactly the same place as the existing dinky bell wire is connected. I enlarged the wire hole in the front of the case, and installed a cheapy "replacement lamp plug" on the end of the cord so I can use a regular extension cord for launcher leads. Use a female plug on the launcher, and then use a male plug and a piece of lamp cord wired into the plug, and then solder brass clips from radio shack on the other end of the lamp cord after seperating the leads about a foot or so back. To seperate lamp cord into seperate leads, just make a small cut through the very end of the wire between the two wires in the little notch between them, then pull them apart-- they'll "unzip" as you pull. Just plug your extension cord male end into the controller plug and the clip end male plug into the other end of the extension cord after pulling it out to the launch pad.

The second launcher is an old Estes POLA-PULSE controller, the kind Estes sold 20 years ago that used the Polaroid flat 3x3 inch square camera batteries. Those weren't around long and were pretty expensive and ill suited to launcher duty, so the first thing I did was swap in a lampcord lead (as with the other controller I did later) to replace the internal battery with clips to connect to the car battery. I hated the bulb on there as well, so I gutted an old VCR I had laying around for LED's and resistors, soldered the resistors directly to the LED legs, and soldered small extension wires (actually the old ignitor lead wires from the thin leads that come with the launcher which is too small (too much resistance which limits current to the ignitors, part of the reason why you can count to zero and hit "launch" and hold the button down on an Estes controller and usually the rocket doesn't launch for at least another half-second or second or so.) The stupid bell wire is just too small for reliable operation, but Estes likes it because it's cheap. If you want a good controller though, this is the first thing that has to go. All I had was two green LED's but that's ok, because I wired one up to directly replace the light bulb using short lengths of wire to connect the LED's to the brass contacts inside the case with ring terminals, and the other green LED is connected up directly across the two external battery wires coming in from the battery charger clips that connect the controller to the car battery. Again be sure to connect the LED's up with the proper polarity or they WON'T light up. Be sure you connect the battery clips correctly too (red to positive, black to negative) or they LED's won't light. The bulbs work either direction, but LED's can only flow in ONE direction. It's not a big deal though once you wire it up. I made another copper key for this controller as well. I used the sharp tip of a test light to carefully scribe the case to tell me what each LED means (just for reference, it's basically intuitive, but it helps when someone else launches for me when I'm taking photos so they know what the LED's do) and then painted a bit of liquid paper into the scribe marks to highlight the letters for easy visibility. The launcher leads are again done away with the dinky bell wire and replaced with lamp cord and plugs for use with an extension cord.

I don't have any wiring diagrams but I could whip some up if you really need them.

Later! OL JR :)What do you think about this? If I use 16 gauge lamp cord, leave the bulb that came with the controller and used a auto jumper pack (12V and 400AMPS), will the bulb blow out or will this setup work? I bought an led repalcement bulf with same base as original elec beam unit had but it won't fit. Thanks----

[Shreadvector]

Original lamp ("bulb") will glow way bright under 12 volts and pass a LOT of current. it can burn out if left on too long.

Use the LED replacements that the pinball folks use:

http://www.pinballlife.com/index.php?p=product&id=1174&parent=192

[gar1948]

Thanks very much for the info. I just ordered the pinball led's as you suggested.
:)

[luke strawwalker]

What do you think about this? If I use 16 gauge lamp cord, leave the bulb that came with the controller and used a auto jumper pack (12V and 400AMPS), will the bulb blow out or will this setup work? I bought an led repalcement bulf with same base as original elec beam unit had but it won't fit. Thanks----

That would definitely help (lamp cord).

Interesting that the replacement bulb won't fit... take a careful look at the bulbs and compare the lengths, diameters, retainer pin locations (little bumps on the side of the bulb that fit into the slots in the bulb receptacle) and compare them all. I'd lay odds that the LED bulb has a retainer pin in a different location or something that's preventing it from going in the socket. If it can be filed off so the other one still fits, it should work. If not, if the diameter is different or it's a LOT longer or shorter or something, then it might not work. You should be able to get an LED bulb to fit it.

The 6 volt bulb will work with the 12 volt input, but like shread said it won't last very long. You can always get a 12 volt bulb to replace it with. The LED bulb has a resistor and generally doesn't care what the input voltage is, so long as it's within reason...

Later! OL JR :)

[UCBadger]

What about the 4 motor Saturn IB? Will the quest launch system with the optional cable to a 6 V lantern battery work?

[LeeR]

Can you describe (or point me to a thread) how to wire in an LED into a 6V (or 12V) circuit? I do mean a standard LED, not one of the 6V LED bulbs also mentioned.

Thanks,
-Tim

This is a useful utility to figure the resistor to use for an LED:

http://www.ledcalc.com

[Shreadvector]

It's really simple: You want your launch system to supply enough current to fire all of your igniters instantly. So, you look at the type of igniters you are using and choose the appropriate launch system.

The Quest Q2G2 igniters require very low current to fire. they are "so fire" rated at 50 mA and "All Fire" rated at 120 mA. SO if you have a 4 motor cluster, you need a minimum of 480 mA. You're wise to use a system that can deliver WAY more than that to be safe.

I measured the current flow delivered by many different controllers, and the results are attached below. The Quest controller with the regular internal battery will work fine, but the EBC and a larger capacity battery will be great. And remember that all 6 volt lantern batteries are not alike. Some have 4 D alkaline cells inside with a spacer on the bottom while others use 4 F size cells and have no spacer inside. The F cells are longer and have more current delivering capability and will last longer.

Quest controller with 9 volt alkaline battery internal:
Continuity current 12.5 mA
Firing current 3.3 A dropping to 2.9 A when held for several seconds. It then rebounds after resting.

Electron Beam with 4 fresh AA alkaline batteris internal:

Continuity: 190 mA

Launch: 2.75 A



Estes E with 4 fresh AA alkaline batteris internal:

Continuity: 210 mA

Launch: 3.72 A initially, dropped to 3.65 A and then rose to 3.75 A as testing progressed (battery heating effects?)



What about the 4 motor Saturn IB? Will the quest launch system with the optional cable to a 6 V lantern battery work?

[BEC]

Fred's results are a little lower than what I got and posted in post 22 of this thread, but they're in the same ballpark for sure. My tests were into a dead short at the microclips (actually shorting the output end of my Power Anaylzer Pro together with the microclips connected to the input end).

I'm still surprised at how much current the little alkaline 9V battery well deliver at least for a short time.