Timed reversing polarity circuit

What are you planning on using to drive the motors?  I would assume you are looking at a 5 wire setup which would take two relays.  What kind of current are you using?  Is the run time always going to be 3 seconds?  What is this for?

I can provide a cheap circuit to acomplish what you are looking for using a programmable microcontroller.  PM me or check out the link in my profile if you are interested in my help.

Good luck!

Pm sent. Thanks Kevin.

Can someone tell me, using the schematic for constant to momentary in relays special applications, what value capacitor would be needed to achieve a 3 sec output?

you would need a 3 second delayed off timer. This one can be made easy.

Then you need to figure out how to hook it to the switch without frying it,

Here is a motor reverse switch circuit.

Like this!

That would have been nice to know when I was designing the circuit. I should have read it better.

I will see if I can come up with another.

I wrote the code tonight but I won't be able to do anything else until I fly back to Dayton, Ohio this Friday.  By Monday I should have something to send to you.

The software is pretty basic, it just monitors the switch input (switch to ground).  If it sees the switch is turned on then it turns on an 'open' output for 3 seconds.  During these three seconds it continues to montior the switch, and if the swich is shut off it will shut off the output and turn on the close output.

If the switch stays in the 'on' position for the full three seconds the 'open' output shuts off and the module waits for for the switch to be shut off.  when it is shut off it ouputs a 'close' signal for 3 seconds.

The only thing I'm not sure about is what will happen if you leave the switch in the 'on' position and shut the car car off?  Do you think that is something that needs to be addressed?  We could set it up to automatically close when the ignition is shut off.  Let me know what you think.

Sound good Kevin.

I dont think we need to worry about the switch being left on and the car turned off. I have a master arm switch that  controls the entire nitrous system and is connected to a constant power source, so the module wouldn't know whether the car was on or not. The master arm switch will provide power to the opener switch, so when the master arm is turned off the opener switch will go open and the module will close the bottle. If I decide that I want to be able to turn the bottle on with the master arm switch off, I can always connect the opener switch to a constant power source.

I'm not sure I know what you meant by "it just monitors the switch input (switch to ground). " You realize that the switch doesn't rest at ground correct? It only supplies 12v when on, and will be open when off.

Also, how hard would it be to change the timed portion to 5 sec? I was thinking about how hard the bottle is to open and close. If the motor took an extra second or so to get the knob moving, 3 sec might not be enough. I have opened and closed it many times with a momentary switch and I have never seen it take more than 2 sec, but since the motor has a clutch, I think a 5 sec output would offer a descent safety net.

Well I spent about 5 mintues in the airport today making the changes.  I got a little lazy with the 5 second delay and we'll have to settle for ~4.92 seconds.  I think that that will be precise enough for our application.  If things go well (which so far today they haven't) I'll have this built and tested tonight.

I have a question for you.

If you have a 'master arm' switch why use a separate switch for the bottle opener?  You should be able to tie my module to the other switch, and whenever you flip on the 'master' arm switch the bottle will open.  Also, do you think it would be a good idea to add an LED output to indicate that the bottle is open?  It would be easy enough to do.  Let me know what you think.

Sometimes it's necessary to have the system armed, but the bottle closed. For instance, I use my purge solenoids to release the pressure from the lines after the bottle has been closed. I think the led output is a good idea. I may or may not use it. The switch for the opener is illuminated when on, so it kinda gives a visual that the bottle is open. I won't be mad if you add features though. Did you get the last pm I sent? I had a couple questions.

OK, the main circuit is built and tested.  Seems to work perfect.  I'm going to add a few more lines of code to address some minor issues that I'm seeing, mainly when you switch from 'on' to 'off' while the open output is still on.  I'm going to put a 0.25 second delay between the different outputs to help protect the bottle opener motor. 

I also programmed in the (-) open feedback output.  Basically, after the open output signal is done (~5 seconds) this output turns on and stays on until you flip the switch back off, then the output shuts off immediately.  I was thinking you can wire this ground directly to the opener switch.  This is a good idea because it is a diagnostic tool for the module.  With it set up this way you'll hit your 'master arm' switch, hit your 'bottle open' switch and then about 5 seconds later the 'bottle open' switch will light up letting you know that the module is working. 

What do you think?

OK, the modules are ready to ship!

Here are a few pics:

The box on the right is the bottle opener module

Yellow: Ignition Power (15amp fuse provided)
Black: Ground
Purple: 12vdc switched open input (bottle open switch)
Orange (-) 100mA open feedback output (use current limiting resistor for LED, or drive lighted switch direct)

The box on the left is a relay pack, containing two SPDT relays.
Green: Bottle Open Output (10A relay)
Blue: Bottle Close Output (10A relay)

After I got it all up and working I went out and picked up a few switches with lights in them.  The (-) feedback outptu is definately cool and works perfectly.

Hows everything look?  I'll send you a PM with more information.

Thanks,

Very professional looking Kevin. Nice work.

I think if you were going to produce something like this to market though, it would be better to incorporate the relays and everything into one module. Just a suggestion. Doesn't bother me though. I think it's going to be really nice, and saves me from having a bunch of relays, and a big wiring mess. Looking forward to trying it out.

Yeah thats the disadvantage to building something with the parts I have on hand.  Unfortunately I doubt that there is a big enough market for something like this to justify hacing custom boards ordered.  We have never ordered less then 100 boards in an order and I don't think we could sell 100 of these very easily!  I'm assuming that most people would rather use the provided switch instead of paying money to use a different switch.

Anyway, they will ship out tomorrow hopefully!

Thanks again,

You're probably right. Most people would be quite content to use the switch provided with the opener. I'm one of those that always has to have something custom. I take a lot of pride in my car being unique. Anyways, I appreciate all the time and effort you put in to this project for me.

Thanks

Just a little update.

I want to thank Kevin Pierson for building a module for me. I could have built a circuit to accomplish what I wanted, but he made it really easy. The module he built is digital, and a lot smaller than what I would have built. The design includes more features than I had even thought of, and the work and communication was very professional. All at a great price too.

Thanks for all your time and work Kevin.

Not a problem!  Thank you for giving me the opportunity to work with you.  Truthfully the entire thing worked out better then I had imagined it would!  Definately a cool little add on to your nitrous kit.

Thanks again, and enjoy!