Help in creating a circuit to produce specific number of output pulses...

Discussion in 'The Projects Forum' started by Daniel454, Jun 4, 2007.

  1. Daniel454

    Thread Starter New Member

    Jun 4, 2007
    3
    0
    Good afternoon to all. I hope this is going to be a simple request as I am sure you all have much more important circuits to work on.

    Basically, long story short, I am working in a 11 - 14V environment (Car) and have a circuit I wish to control that requires MULTIPLE input pulses to activate, but I want to trigger it with a single pulse from 3 different switches...

    The circuit I am controlling has a single line in, where it is expecting either 5 pulses, 7 pulses, or 9 pulses within a certain time frame to activate one of three modes.

    However, I happen to have a 3 momentary switch panel already installed which I would like to use to control this circuit.

    Ideally, I want to be able to press button 1 and release, triggering this new circuit which will output 5 12v pulses to this other circuit... Then If I press button 2, it would accept this as a seperate input and trigger 7 pulses on the output, etc.

    I would be ok with the idea if I had to actually have 3 seperate curcuits if one circuit with 3 inputs could not be built... I could simply diode isolate the outputs and still run them all into the existing system... But prefer one to do it all just for simplicity.

    So, what, if any options do I have? I have searched all day on circuits and hobby kits I might could adapt to this, with no luck. I really do not mind spending some money on this so it doesnt even have to be a made from scartch circuit unless that is the only option.

    P.S. My "electronics engineering" is, well, rusty to say the least...
     
  2. chuckey

    Well-Known Member

    Jun 4, 2007
    75
    10
    You do not say what sort of pulses you are generating or at what speed. The way I would approach this is to have 3 SR bistables controlling one counter with the output lines decoded at 5/7/9 pulses , when the button is pushed its SR bistable is set. The setting of any SR allows the counter to run. The correct decoded count output is used to reset the SR. This will then stop the counter.
    The gate count should be 2 gates/SR = 6, 4 gates to get the "set" function, 1 counter, 2+3+3 gates for the decoding. + what ever your clock generator is.
    Frank
     
  3. Daniel454

    Thread Starter New Member

    Jun 4, 2007
    3
    0
    Sorry about not giving all the needed info. I was trying to keep it high level enough to keep it simple, but did not mean to leave anything out...

    The pulses need to be 12V, and probably about 1 ~ 1.5 second in length each with the same time in between. They will be feeding a low amp control circuit so they will not have to sustain any large amount of current draw.

    I am thinking your direction is a feasible one, as we look into this more, I will need at least a base line schematic if possible, doesnt have to be perfect detail but at least to give me the direction and options.

    Thank you much for the help!
     
  4. ashokcp

    Active Member

    Mar 8, 2007
    50
    2
    A simple microcontroller can be used. The output needs to be converted to 12V, no problem to the input to this circuit as they are only key switch inputs. Depending on the input key pressed, the program can send out the no. of pulses required.
     
  5. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi..I can do this for you...Just give me a few days, as much info as you can, and I will sort it out.I will do it with a PIC micro.....(PIC16F84 or 16F628)I will need to know what your output requirements are (high pulses, or low)and also the voltage from the switches (or are the switch contacts all avalible).....(attive high or low).....The more info, the better......I can supply you the PIC, programmed, and the schematic, but I won't have enough time at the monent to do a PCB, or construct it, as I am doing quite a few other projects.....Speak soon......Daniel.
     
  6. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    An 8 pin pic will do nicely, or a 4017 and a couple of quad NOR (4001) chips set up as 3 RS flip flops and a 2 NOR gate oscillator, a few diodes, some resistors and a cap or 2.
     
  7. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Yes you are rite.... PIC16F628."too many pins"And yes, you are rite again "4017 + gates !!!!..... That is how I would have done it BP (before PIC's).....Daniel.
     
  8. Daniel454

    Thread Starter New Member

    Jun 4, 2007
    3
    0
    Wow, THANKS GUYS, this is GREAT!

    OK, more info... The switches I am using, we have full access to, meaning in and out for each switch. So, we could use them to switch and supply ground, positive, or whatever... I have 3 momentary switches, 6 connectors/contacts and none of them are currently tied to ANYTHING so it is fair game.

    The final, pulsed output has to be 12V positive in respect to a vehicles ground. I am sure I could use relays to convert it if it was easier to output ground or negative pulses, but the click of a relay will be quite annoying.

    I have confirmed now that the pulses have to have no more than 1 second delay in between each pulse... As the system I am activating is programmed to ignore pulses if more than a second lapses between inputs. So we should shoot for just less than 1 second pulse on, then just less than 1 off, etc....

    Also, looks like I had the number of pulses incorrect, one button input should trigger 3 pulses, one should trigger 4 and would should trigger 5 pulses out.


    OK, so let me back up and punt again...

    --> Everything runs fom a vehicle power source, so the circuit should be able to handle anywwhere between 11 ~ 14 Volts.

    --> 3 Momentary switches, have full access to both contacts on each switch.

    --> Circuit should have 3 seperate inputs, one for each switch

    --> When button 1 is pressed, the circuit should output 3, 12V (high) pulses out.

    --> When button 2 is pressed, the circuit should output 4, 12V (high) pulses out.

    --> When button 3 is pressed, the circuit should output 5, 12V (high) pulses out.

    --> Circuit preferrably only has one output line, however, I can handle diode isolation after the fact if necessary


    --> One more possible option???? While I can get what I need done with the above control circuit, I have also found that additional features are available with 6, 8, and 10 pulses... I was thinking I could just press button 1, wait a few seconds and press it again, and this would be 6 pulses out, but since timing would then be critical, is it possible for this circuit to accept 2 presses of button one and output 6 (double the) pulses out without me having to wait and time it just right, or is that getting WAAAY to difficult? I only have 3 switches available (stock location)....


    Does this give you the full idea or did i miss something?

    Oh, just in case you want to know, the switches I am using are unused switches built into the car door... they were intended for a feature I do not have on my car, but they do function fine, I just have to create a wiring harness... And the SYSTEM I am driving can be seen here:http://www.noesp.com/images/coolit_install.pdf. He originally designed this system to be activated by turning on and off your parking lights in the car, but since I have these switches available doing nothing, I like the idea of using them instead....
     
  9. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi...I will write the code this week, and test it over the weekend.PM me your details and I will send you all the schematics and the micro all programmed up.....Daniel.
     
  10. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi mate..Rite!I have writen the program...The way I have done it is that after the press (and on the rellease) of each switch, the micro waits for 1 second and then sends the pulses.During that 1 second wait, the micro looks for another switch press, if ther is another one within that second it will ignore the first and output the number of pulses for the second.I.E: switch 1, 1 click = 3 pulses....switch 2, 1 click = 4 pulses....switch 3, 1 click = 5 pulses....switch 1, double-click = 6 pulses....switch 2, double-click = 8 pulses....switch 3, double-click = 10 pulses....I have set the pulses at 700mS...Q.1. will 1 second wait for double click be long enough ?Q.2. is 700mS O.K. ?Q.3. is that the order that you want them in ?Speak soon.....Daniel.
     
  11. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    Hi...This is all done, and on its way to you in the post..Nice little project to do....Daniel.
     
  12. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    As I said in my last reply... This is done !!!

    Just in case anyone is curious as to how It turned out, here are the PDF's....

    Daniel
     
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