The other way, the igniter connected portion will not function until all of the ARM switches are closed.

I thought that was the purpose of the switches. Your circuit works perfectly without them. They seem to be more of a show thing than anything else. I guess I should have asked the purpose.

 

Hi Guys -

I'm very sorry to say this, but now I'm getting confused

Would it be possible for one of you to send me a revised drawing showing me what you mean ? So, I take it you're saying to wire the 3 toggle switches between the fuse & the R1 resistor. Not sure what you mean by the J1 cutoff switch. I realize that the number of switches I have is way overkill (my son likes to push buttons what can I say) so in part - yes - it is for prettiness & show. If they make things too complex and overburden the circuit, though, then I'll only use one switch coupled with the stereo plug for my 'ARM' circuit - would be preferred to use 3.

All the switches are rated @ 12v and they are all toggle switches. The launch button is a 12v illuminated push button (game type switch).

I went to Radio Shack this weekend and picked up a 1/4" stereo plug and jack along with a few resistors, a roll of speaker wire, and a fuse holder (couldn't find any 5A fuses though). I also picked up a 12v lead-acid motorcycle battery. I'm planning on building the whole thing up in a nice mahogany box with a lexan top (I'll take some pics and post it when it's finished)

 

Sorry, there have been a LOT of people asking for help lately, and I just completely forgot about it.

See the attached.

I added a "Blown Fuse" indicator, too.

There is no logic for the sequencing of the three switches. However, they all must be ON, the ARM key in, and both launch buttons pressed simultaneously in order to provide current to the igniter.

Adding logic for the sequence would just really complicate things.

 

I've been thinking of cluster ignition, and continouty checks. If I can I'll draw something else, I'll probably put it another thread.

Let us know how it goes, all of us like feedback.

 

Hi Sgt. Wookie, et.al. -

Thanks!! This new circuit diagram you've provided looks terrific and I'll give a whirl

So last night, I took apart the controller that my son & I put together and drew its schematic (please see attached). I also took my multimeter and attempted to ckech voltages, resistance, and amperage throughout. I must say I became quite perplexed at my findings.

At the source I was getting 12.5 volts. At the igniter contacts I saw a huge drop to 6.5 volts and when the launch switch was depressed then this value jumped to 9.5 volts. However, I only read about 5-6 milliamps at the igniter contacts (I think the typicaly Estes igniters require about 30mA).

Unfortunately, I think I zorched the Amp checking part of my meter though, because after doing these tests I couldn't ever get it to give me a reading again....don't know what I would've done to damage it....any ideas?

What was really perplexing to me though was that no matter what I did, I was not able to check resistance at any point in the circuit. I was able to check continuity....not resistance. The meter would only display "OL". Since all of my parts are typical Radio Shack parts I have no functional info about them except for their volt/Amp ratings. I'm pretty sure that the 2 12v lamps I have wired 1) to show that the power is on and 2) for continuity are both LEDs with a resistor wired in, but they're all encased and I can't see the color bands very well. That being said, though, I still don't get why I'm not able to check resistance?

 

I've converted your Word document to a .png format image file; it's much easier and faster to open that way; it can be viewed in a web browser with no extra software required. Your original is on the left; a corrected version is on the right.

Your circuit on/off indicator lamp is connected in series with the igniter. That would prevent the igniter from receiving the current necessary to ignite the engine.

The lamp should be connected between the junction of the ON/OFF switch and the ARM switch, and the battery negative terminal. See the corrected version on the right.

You probably attempted to measure current at too low of a setting, and blew the meter's internal fuse. Usually, meters have a 250mA fuse. You will need to check yours.

[eta] Igniter current - I found this .pdf document: http://www.gwiz-partners.com/igniters.pdf
Estes igniters are documented on page 7; peak current was 12.3A for 30mS.

If 12.3A current is not available, it will take considerably longer than 30mS for the igniter to get hot enough to light the engine.

 

Hey that's cool!
If I need to post an attachment again I'll try to remember to convert the file. Thanks for the tip.

I think my meter case is sealed so I'll have to see if I'm able to open it somehow to replace the fuse.

Thanks again!

 

Sirius.Black

I have read your thread with keen interest. I have never been involved with model rocketry but have always wanted to do so. It looks like great fun and is a great father son/daughter endeavor.

I believe the purpose of the multiple switches is to make it more realistic. (like NASA does it) And in that vein I propose to give the switches actual purpose. I’ve taken the liberty to modify SgtWookie’s diagram. The diagram (attached) goes with the legend below.

If anyone sees any errors, by all means, please speak out.

Hope it all makes sense.

williamj

Vs ----------------------------- 12 Volt DC
Key 1, J 1 ------------------- Master Systems Key
Fuse --------------------------- 5 Amp
D 5 ----------------------------- Blown Fuse Indicator
R 1, R 2, R 3 --------------- 680 Ohm
S 1 ----------------------------- Systems Enable Switch
L 1 ----------------------------- Systems Enable Indicator Light
S 2 ---------------------------- Systems Enable Check Switch
L 2 ---------------------------- Systems Enable Check Indicator Light
D 4 ---------------------------- System Continuity Check Indicator (on/yes off/no)
D 1, D 2, D 3 -------------- Visual Warning (Launch In Progress)
S 3 ---------------------------- Launch Count Down Enable Switch
L 3 ----------------------------- Launch Count Down Enable Indicator
BZ ----------------------------- Launch Count DownEnableAudibleWarning
---------------------------------- (countdown in progress)
---------------------------------- (perhaps on one second intervals for easy count down)
Key 2, Key3 --------------- Launch Keys (NOT interchangeable)
PB 1, PB 2 ---------------- Launch Buttons
AC 1, AC 2 ---------------- Igniter Connection (alligator clips)

​

 

Ooops, sorry, forgot the attachment.

williamj

 

Well, that would work.

A few comments;
1) You have used the reference designator "L2" twice, once by R2, again below BZ. Reference designators should always be unique; otherwise their very purpose is defeated.

2) You have "Key 2" and "Key 3", but no "Key 1". It's best if reference designators start off with 1, and increase by 1; otherwise people wonder where the missing part is.

3) You have BZ wired in series with L2. While the BZ may require current limiting, a 12v incandescent lamp will not. These two items should be in parallel. The BZ may require a resistor in series with it to limit current; somewhere around 470 Ohms to 560 Ohms. Someone else had a related project recently, they used a 560 Ohm resistor successfully in series with a piezo buzzer. Your mileage may vary.

4) You have the left L2 in parallel with D1/D2/D3/R2. This is a bit redundant to have multiple indicators for the same condition.

5) The buzzer should sound only when both Keys are inserted. To this end, both Keys should be moved to where S3 is. Otherwise, the buzzer/armed light will soon be disregarded as a false "armed" indication.
(I like the idea of two removable keys, BTW - one for Dad, one for munchkin. )

 

Hi Guys -

Boy you all have been tremendous help with your ideas and suggested improvements!

WilliamJ - You are absolutely right that model rocketry is a wonderful father daughter/son hobby. For one, it's not very expensive to get started in especially with all the really nice complete ready-to-fly starter sets on the market today; for another, flying the rockets really only requires a nice open field or decent park; and for a third, there's no limit to what a person is able to do in model rocketry from experimenting with your own launch controller, building your own launch pad & equipment, designing your own rockets, and then of course participating in all sorts of great competitions. Some of us advanced 'rocketeers' play around with all sorts of on-board instrumentation as well as flying the monster high-power ships! My son has really taken a great interest in the sport and we flew his ESTES Oracle rocket the other week which has an on board color video camera on it and that was just the coolest thing!

Personally, I'm just not the skilled in designing circuits I am able read and interpret the schematics but only have a rudimentary knowledge of circuit functionality.

Sgt.Wookie - FYI,

I took the revised schematic you gave me yesterday and rewired my 1st launch controller. As a result the amperage doubled but was still insufficient to torch the igniter. So I took out the 2nd redundant 'arming' switch which must've required significant current draw for its lamp and then the controller worked fine. I don't know what the final amp output was though because when I retested the circuit it blew the fuse in my other meter....must be greater than 200mA though!

 

WilliamJ - You are absolutely right that model rocketry is a wonderful father daughter/son hobby.

I concur. Dad got involved with my model rocket hobby right after i blew up the kitchen trying to make rocket fuel. On a trip out west in '66, one of the highlights was a trip to the Estes factory in Penrose, CO.

I still enjoy watching rockets blast off. I can see the Shuttle launches from the Cape from my backyard. This was Senator Glenn's return to space:

Yesterday's shuttle launch was only visible for about a second due to the clouds.

I took the revised schematic you gave me yesterday and rewired my 1st launch controller. As a result the amperage doubled but was still insufficient to torch the igniter. So I took out the 2nd redundant 'arming' switch which must've required significant current draw for its lamp and then the controller worked fine. I don't know what the final amp output was though because when I retested the circuit it blew the fuse in my other meter....must be greater than 200mA though!

Ack!
Don't try to measure the current from your controller with an ammeter; you will fry it.

After reviewing the PDF document regarding various types/brands of igniters yesterday, the ratings of the pushbuttons and fuse will need to be increased. The Estes igniters have a resistance of about 1 Ohm, which means a current of about 12.3 Amperes for around 30mS.

You might get by with a 10A slow blow fuse. In any case, the switches and wiring must all be rated for no less than the fuse used.

That is one of the reasons why I was reluctant to include all of the extra complexity.

If you tried to measure the current available without an igniter in place, the current would be limited only by the resistance of the wiring and switches.

If you want to measure the current available at the launch pad end, then I suggest you obtain a precision 1 Ohm resistor that is rated for 50 Watts.
Connect the resistor across the alligator clips.
Connect the meter across the resistor, set to read on the 20V scale.
Since I=E/R (Current in Amperes = Voltage/Resistance in Ohms), the voltage reading on the meter will be the same as the current flow in Amperes.

 

That explains the meter problem ! Well...luckily I can replace the fuses in the meters.....chalk this one up to experience
Your idea of putting the resistor across the alligator leads is another...duh...moment for me. I should've thought of that. Ohm's law comes in handy there certainly.
Fortunately, I had already taken the fuse rating into consideration of the other components and have a 10A fuse. I will likely be increasing this though.
My 11-year old (who wants to be an astro-physicist) is tickled pink with his homemade controller and can't wait to try it out this weekend. I'm planning on trying it out with my ESTES Maxi-Force w/ a 3-D engine cluster. I'll let y'all know how it works out.

I was in Dunedin, FL as a young boy and watched the night flight of Apollo 14 hit the evening skies. Simply spectacular! If you ever get the chance (probably have already) get over to the Cape for the tour of the Kennedy Space Center...WOW!

 

What part of the country are you Sirius?

 

Hi Bill -
I live in Northern California on the East Bay side of the San Francisco / Oakland / San Jose (Silicon Valley) region. How about you?
Tom

 

That explains the meter problem ! Well...luckily I can replace the fuses in the meters.....chalk this one up to experience

I've given up on expensive meters; it's too traumatic when they get broken/stolen/lost. I spent $200 on a really deluxe model a decade ago; within a year it was a paperweight. Nowadays I just use cheap DMMs that regularly go on sale at Harbor Freight; you can get them for under $3, and they're surprisingly accurate.

I tested a couple of them using a $20,000 Fluke Calibrator; their readings were within 1% of the actual values - plenty good enough for hobbyist use. I have four of them kicking around here. They're so cheap it's almost less expensive to buy a new one than replace the 9v "transistor" battery.

Radio Shack stocks a number of fuse types, but be prepared to pay around $4 for a 4-pack of fuses there.

Your idea of putting the resistor across the alligator leads is another...duh...moment for me. I should've thought of that. Ohm's law comes in handy there certainly.

It's really not all that obvious until you think about it for awhile. Even experienced people occasionally blow a meter's fuse. I keep several fuses handy, but once in a blue moon I'll still blast one to smithereens.

Fortunately, I had already taken the fuse rating into consideration of the other components and have a 10A fuse. I will likely be increasing this though.

The fuse must be the "weakest link". It is there to protect all of the other components. If something else in the circuit winds up being rated for less current than the fuse, it will protect the fuse by melting/vaporizing first.

My 11-year old (who wants to be an astro-physicist) is tickled pink with his homemade controller and can't wait to try it out this weekend. I'm planning on trying it out with my ESTES Maxi-Force w/ a 3-D engine cluster. I'll let y'all know how it works out.

OK, this falls directly in line with the maximum ratings and that igniter test PDF. If you are going to have three igniters in parallel, instead of a single 1 Ohm load, you will have a 1/3 Ohm load. With 12v applied across a 1/3 Ohm load, that results in a current of 36 Amperes. I'll bet you weren't counting on that.

So, you will need a way of ensuring that the current does not exceed the ratings of your switches, wiring, etc.

One of the easiest ways to do that would be to include a power resistor in series with the wiring to the launch pad. To limit the current to 10A, you would require a resistance of 1.2 Ohms. The 20+ feet of 16 gauge wire has some resistance already, so you could use a 1 Ohm power resistor rated for 10W or more.

It will take somewhat longer for the igniters to get hot enough to fire the engines, but we're talking about a difference of much less than 1/5 of a second.

I was in Dunedin, FL as a young boy and watched the night flight of Apollo 14 hit the evening skies. Simply spectacular!

As a young lad, I was glued to the TV for the Mercury, Gemini and Apollo missions, 1,100 miles from the launch sites. They made a huge impression on me.

If you ever get the chance (probably have already) get over to the Cape for the tour of the Kennedy Space Center...WOW!

I have! Those F1 engines used on the Apollo 1st stage dwarf a human, but still - it's practically incomprehensible to consider that those engines were capable of producing 1.5 million pounds (750 US tons) of thrust apiece, for a total thrust of six million pounds, or 3,000 tons of force.

As a comparison, an hydraulic press used to forge complete parts from a blank of steel might use 30 to 60 tons of force. Just one of those F1 engines generates more than 12 times that.

 

Hi Bill -
I live in Northern California on the East Bay side of the San Francisco / Oakland / San Jose (Silicon Valley) region. How about you?
Tom

Bill is near Dallas, TX
I'm in Orlando, FL

It's a good idea to put your general location in your profile; that way people can give better tips on where to go to get stuff.

Silicon Valley is a fantastic place to find surplus stuff. But be careful, or you will wind up having to park your vehicles in the street, as your garage will be full of "cool stuff". Ask me how I know this.

 

Thanks for the comments and observations SgtWookie, they are much appreciated.

1) You have used the reference designator "L2" twice, once by R2, again below BZ. Reference designators should always be unique; otherwise their very purpose is defeated.

Done

2) You have "Key 2" and "Key 3", but no "Key 1". It's best if reference designators start off with 1, and increase by 1; otherwise people wonder where the missing part is.

Key 1 is located in the upper left hand corner of the drawing, it is nothing more than a battery disconnect.

3) You have BZ wired in series with L2. While the BZ may require current limiting, a 12v incandescent lamp will not. These two items should be in parallel. The BZ may require a resistor in series with it to limit current; somewhere around 470 Ohms to 560 Ohms. Someone else had a related project recently, they used a 560 Ohm resistor successfully in series with a piezo buzzer. Your mileage may vary.

Done

4) You have the left L2 in parallel with D1/D2/D3/R2. This is a bit redundant to have multiple indicators for the same condition.

I was under the impression that L 1, L 2, and L 3 were panel mount and the Led array was more for public awareness. A rocket launch draws conciderable attention and I had envisioned the led array and siren (BZ) mounted so as to keep the observers informed of launch status.

5) The buzzer should sound only when both Keys are inserted. To this end, both Keys should be moved to where S3 is. Otherwise, the buzzer/armed light will soon be disregarded as a false "armed" indication.

Done

I know that this is a convoluted way to do this but I believe that the young need to realized that somethings, for safety's sake, require checks and balances and procedure.

thanks again

williamj

 

I know that this is a convoluted way to do this but I believe that the young need to realized that somethings, for safety's sake, require checks and balances and procedure.

thanks again

williamj

D1, D2, and D3 wired in series with a 680 ohm resistor (R2) will be pretty dim.

Check the specs of your leds, but 3 leds with a forward voltage rating of 2.2v and a current draw of 20ma will only require a 270 ohm resistor when wired in series with a 12 volt source.

 

Hi Guys!

Happy Holidays Hope y'all got as stuffed as my turkey was!

I wanted to proved a bit of an update.....

So I modified my original circuit (1st attempt) and it now works beautifully! The current draw on my second 'ARM' switch w/ lamp was too excessive, though, and so I removed it.

We took it out last weekend for a launch of my Estes Maxi-Force, which had a 3-D cluster and it fired right up w/o a hitch...plenty of juice coming from those 8 AA batteries.

I'm still waiting for my LED array to come in as it was back-ordered. However, if it helps with the circuit design here is the link to it....

http://www.action-electronics.com/scanner.htm

The one I ordered is the blue array that is about half way down the page. In the photo it looks as though it has 7 LEDs.

Tom