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Lastly, I have begun on a schematic of the wiring at the launch rack end of things. This one happens to be for a MMX rack but I envision most of the LPR systems as being substantially the same.

1. The connector is the opposite end of what is at the controller. pins 1-8 handle the switch activated current for pads 1-8 respectively. Pin 10 is the negative and I have used pin 9 to carry current to activate a light and a buzzer on the rack to show that this cluster is active when the cluster switch is closed.

2. notice that the jacks are 1 per pad and that the rack has 6 pads. It also has connections for 2 satellite pads.

3. the big issue for me at this point is continuity indication at the pad. I would like for each pad to be able to hit a momentary switch and check for continuity at hookup and do so SAFELY. Unfortunately, I have no idea how to accomplish this and my schematic indicates as much.

Help, please.

mmx-1a.jpg
 
I'm open to suggestions. How would you recommend achieving the stated goal with a different wiring scheme?

Well without getting into too many details, isolate the individual continuity circuits with some fast switching diodes. Add a transistor switch (PNP I think) to drive the piezo. With the right layout it will work. But is this really what you need?
 
I appreciate the input. Let me address the reason for the buzzer first. To me, an audible tone is more noticable than an LED, no matter how bright the LED may be and will draw attention that something is amiss (or ready to launch). My assumption in the schema I described is that as rockets are launched the buzzer will stop because either the igniter burned through or the Sw3 is opened after the launch. THe intention is not to let all of them stay closed until everything is launched; the plan is for the switch to the appropriate pad to be closed when needed and then reset after launch. In fact, one of the few pieces of hardware I actually have bought is the switch covers. Closing them opens the switch.

I understand the warning about current flowing through the buzzer to reach the igniter and bypassing Sw1 and Sw. Isn't that handled by the proper choice of the buzzer, a low current one?

I agree that the buzzer will draw attention, but I don't think this will work the way you described it earlier. If there are igniters connected, the buzzer will sound as soon as any SW5 switch is closed. The more igniters connected, the louder the buzzer will be. That will happen with all the SW3 switches still open because the current will flow throught the R1/LED1 leg for each pad, bypassing the SW3 switch.

As for the low current buzzer, that can work both ways. If your R1/LED1 combinations are set up to flow 10 ma and you have 8 igniters connected, you will get 80 ma flowing through the buzzer when the SW5 switch is closed. 240ma if you close all the SW5 switches with full racks. If the buzzer will only allow, let say 16ma, then you will only get 2ma through each LED if only one SW5 is closed, which might not be enough to light the LEDs. Also, the buzzer may not limit the current. It may allow as much current through as you want until it burns out itself. If you increase the size of the buzzer enough to handle the max possible current and allow the LEDs to show continuity, then you will almost certainly be able to fire low current igniters like the Quest igniters by closing SW3 without using SW1, SW2, SW6.

What I'm getting at is that using the buzzer for all pads like you have it wired can work just like the lamp in the Estes controllers. It works fine for Estes igniters, but if you use a new Quest igniter, the lamp can cause the igniter to fire. I just don't see the buzzer working safely the way you have it connected.

I would highly recommend you breadboard the SW1, buzzer, SW5, and eight SW3 switchs with R1/LED1 and test them with the Quest igniters to make sure it works the way you want before you go through the time and expense of building the whole system. Make sure you try it in as many conditions as you can, 1 igniter, 8 igniters, 4x clusters, etc.
 
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If the purpose is to read the firing current, it won't be fast enough.

John, you'd be surprised just how fast an analog ammeter can register the current - plenty fast to get a good idea of how much current is being drawn on average.

But, was said - it's an extra bell and whistle that's not absolutely necessary.
 
John, you'd be surprised just how fast an analog ammeter can register the current - plenty fast to get a good idea of how much current is being drawn on average.

It'll jump when the launch button is pressed, but it won't tell you much. A meter is an inductive device and will resist the change in current. You'd need an active circuit to do a "peak hold" for it to be useful. A good indication of sufficient current is the rocket taking off into the air. ;)

-John D
 
As for the low current buzzer, that can work both ways. If your R1/LED1 combinations are set up to flow 10 ma and you have 8 igniters connected, you will get 80 ma flowing through the buzzer when the SW5 switch is closed. 240ma if you close all the SW5 switches with full racks. If the buzzer will only allow, let say 16ma, then you will only get 2ma through each LED if only one SW5 is closed, which might not be enough to light the LEDs. Also, the buzzer may not limit the current. It may allow as much current through as you want until it burns out itself. If you increase the size of the buzzer enough to handle the max possible current and allow the LEDs to show continuity, then you will almost certainly be able to fire low current igniters like the Quest igniters by closing SW3 without using SW1, SW2, SW6.

I believe you might be right if this was to be an electromechanical buzzer. Except it it's a 12v buzzer it's only going to draw what current it will, not burn out. Different story if it is a 6v buzzer, for example. But I believe the plan was to actually use a piezo.

Small sonalerts are rated to draw up to around 12 ma at 12v. So that's an internal impedance of what, 1200 ohms or so. At 10 ma a high brightness LED will drop maybe 1v, maybe a little more or less. So the piezo now sees 11v so it will draw slightly less current. Add more LEDs in parallel and their overall impedance drops, first to 1/2, then 1/3, etc. So slightly more current to the piezo yes, but now current is being divided among the LEDs. With 4 LEDs in the circuit each will see only 1/4 of the current of 1. And all will be much dimmer as a result. But the piezo will be ok. The effect on the LEDs will be dramatic and noticeable. That's why I thought isolating the the piezo or moving it somewhere else in the circuit made sense.
 
If you haven't already, take a look at this controller. The Pelican case is a nice luxury. https://www.vernk.com/LaunchController.htm and while your at it, just as well take a peek here https://www.vatsaas.org/RTV/Support/ControllerIndex.aspx

I like Vern's site. He does great work. I had not seen the second link before. Thanks. Lots of good info there on controllers actually built, along with construction techniques.

Here's one of mine, just to give a sense of how things can be laid out. This is a cheap toolbox from Fry's.

IMG_3504.jpg
 
I believe you might be right if this was to be an electromechanical buzzer. Except it it's a 12v buzzer it's only going to draw what current it will, not burn out. Different story if it is a 6v buzzer, for example. But I believe the plan was to actually use a piezo.

Small sonalerts are rated to draw up to around 12 ma at 12v. So that's an internal impedance of what, 1200 ohms or so. At 10 ma a high brightness LED will drop maybe 1v, maybe a little more or less. So the piezo now sees 11v so it will draw slightly less current. Add more LEDs in parallel and their overall impedance drops, first to 1/2, then 1/3, etc. So slightly more current to the piezo yes, but now current is being divided among the LEDs. With 4 LEDs in the circuit each will see only 1/4 of the current of 1. And all will be much dimmer as a result. But the piezo will be ok. The effect on the LEDs will be dramatic and noticeable. That's why I thought isolating the the piezo or moving it somewhere else in the circuit made sense.

I wasn't sure about how the buzzers worked. I know you have to have a buzzer with a build in oscillator rather then just a piezo speaker. I wasn't sure how the buzzers were set up for current limiting. Since they do limit the amount of current they allow through, they can be used in line with the igniters without causing the igniters to fire.

From your comments, besides affecting the continuity LEDs, you seem to agree that the buzzer will sound as long as a bank is activated with the SW5 switch and there is at least one igniter with continuity.
 
I wasn't sure about how the buzzers worked. I know you have to have a buzzer with a build in oscillator rather then just a piezo speaker. I wasn't sure how the buzzers were set up for current limiting. Since they do limit the amount of current they allow through, they can be used in line with the igniters without causing the igniters to fire.

From your comments, besides affecting the continuity LEDs, you seem to agree that the buzzer will sound as long as a bank is activated with the SW5 switch and there is at least one igniter with continuity.

Yes I agree the piezo will sound when the cluster is active and any ignitor connected.

If I remember right old DC buzzers, the angry sounding kind, used a coil and an element kind of like in a relay to move back and forth. The motion would make and break contacts energizing and deenergizing the coil, making the element move, which is also attached to some kind of sounding thing, maybe just a piece of metal.

Then there were electronic buzzers (less angry sounding) which used an oscillator and little speaker element and later still the piezoelectric type which replaced the speaker coil and magnet with a crystal element.

I think the old angry buzzers which no one would use anymore would draw the most current, next the speaker type, and last the piezo type. The latter being about 8-12 ma according to datasheets. Amazing the level of sound you get for that too. Annoying as it is. I put lots of tape over mine for testing.

:snowman:
 
I think I'm beginning to see the problem with all that stuff in //. If I understand right, it should not be a problem when you want to launch 1 or 2 rockets but if you were doing a mega launch with all 98 scouts going at once, you would have a lot of current going through the system and divied up all over the place.

I'm going to take a step back and try to read up on some more advanced circuitry to see how to handle this better. Unfortunately for me, the doorbell circuit in the textbooks IS advanced.

I'm going to keep throwing things out here and some day, I will feel confident enough to actually start cutting holes in my enclosure.

Picture-001.jpg

Picture-004.jpg

Picture-005.jpg
 
Now that's a nice box. Looks pricey so I hope you got it for low/no $$ lol.

One thing you might consider is go ahead and mount some switches and LEDs and all that but leave the wires long for now. Use a breadboard like Bone Daddy was showing and try out your circuits completely before committing them to soldered wiring in the box. 22awg stranded wire will go into a breadboard just fine if you carefully tin the end. Your box is big enough that you can have several breadboards in there if needed.

With a breadbard you might even go as far as to try a few diodes and transistors to spice things up a bit.
 
Now that's a nice box. Looks pricey so I hope you got it for low/no $$ lol.

One thing you might consider is go ahead and mount some switches and LEDs and all that but leave the wires long for now. Use a breadboard like Bone Daddy was showing and try out your circuits completely before committing them to soldered wiring in the box. This way you can try different things or even start over very easily. 22awg stranded wire will go into a breadboard just fine if you carefully tin the end. Your box is big enough that you can have several breadboards in there if needed.

With a breadbard you might even go as far as to try a few diodes and transistors to spice things up a bit.
 
JAL3 soon you will have a collection of wire, leds, switches, screws etc. in what we proudly call our junk box. My wife laughs because I take aprt everything that dies, looks like it might die (or anything else that gets in the way off my screw driver.) and scarf out parts.

Here's one of my wire crates. A bit of a rat's nest,. but no worth the effort to sort. I just grab out what I need. I have a nice selection of screws too.

I use solid core copper telephone wire when I breadboard. It's a little thinner than standard breadboard wire. EG sells the real stuff and I think Fry's does also.

My friends and I scarf up every old PC we can. The led and switches with standard pin female connectors are the pot of gold inside an old PC. Pretty ironic that an old computer that sold for $2,000 or so is worth a few leds and switches.

Wire Box post.jpg
 
I guess I never got this posted.

LED, buzzer and igniter all in parallel.

Works great.

See how much fun a breadboard can be?

Keep in mind that a typical buzzer will work with more or less voltage that specified. The one on my breadboard is rated at 12v. It screams like a banshee on 5v.

Let me know if you need a buzzer recommendation.

buzzer led igniter post.jpg
 
JAL3 soon you will have a collection of wire, leds, switches, screws etc. in what we proudly call our junk box. My wife laughs because I take aprt everything that dies, looks like it might die (or anything else that gets in the way off my screw driver.) and scarf out parts.

Here's one of my wire crates. A bit of a rat's nest,. but no worth the effort to sort. I just grab out what I need. I have a nice selection of screws too.

I use solid core copper telephone wire when I breadboard. It's a little thinner than standard breadboard wire. EG sells the real stuff and I think Fry's does also.

My friends and I scarf up every old PC we can. The led and switches with standard pin female connectors are the pot of gold inside an old PC. Pretty ironic that an old computer that sold for $2,000 or so is worth a few leds and switches.

Oh man, I wish I had a good chunk or two of old 25/pair telco today. Great for ematches and ignitors. And launch controllers too of course. A few years ago I had no use at all for it.
 
JAL3 soon you will have a collection of wire, leds, switches, screws etc. in what we proudly call our junk box. My wife laughs because I take aprt everything that dies, looks like it might die (or anything else that gets in the way off my screw driver.) and scarf out parts.

Here's one of my wire crates. A bit of a rat's nest,. but no worth the effort to sort. I just grab out what I need. I have a nice selection of screws too.

I use solid core copper telephone wire when I breadboard. It's a little thinner than standard breadboard wire. EG sells the real stuff and I think Fry's does also.

My friends and I scarf up every old PC we can. The led and switches with standard pin female connectors are the pot of gold inside an old PC. Pretty ironic that an old computer that sold for $2,000 or so is worth a few leds and switches.

I can be a packrat that way for lots of other things, including rockets, but saving mysterious little electrical parts has never been one of my habits. I might need to change.

On another note, I have not abandoned this project. I am just getting the benefit of a real EE type who lives nearby and has agreed to tutor me and help with the design.

I feel soooo sorry for him.
 
I guess I never got this posted.

LED, buzzer and igniter all in parallel.

Works great.

See how much fun a breadboard can be?

Keep in mind that a typical buzzer will work with more or less voltage that specified. The one on my breadboard is rated at 12v. It screams like a banshee on 5v.

Let me know if you need a buzzer recommendation.

I might have to invest in one of those. I knew about them but never had the desire before.
 
Oh man, I wish I had a good chunk or two of old 25/pair telco today. Great for ematches and ignitors. And launch controllers too of course. A few years ago I had no use at all for it.

You know as well as I do that the minute you throw something out, you need it.
 
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