newbie needs help with pulse system

[joe_rocket]

I'm new to electronics and searching google I found this forum.

I am wanting to build a two part system that will have two out puts, one input.

the system is a 12v dc auto system
the input side will be a pulsed ground, up to 5000 pulses per minute.

from that i'd like to do these two things.

for one I'd like to have a knob that will adjust the system using a variable capacitor?
it will measure the pulse rate, and if the pulse rate is to high it will trip the output to ground.


the second I'd like to do is have the same basic setup, using a knob (again a variable capacitor?)
that would set the output. I want the system to take the pulsed ground signal and also send out a pulsed ground, but vary the output by the pulse duration (maintaining a constant pulse rate), the lower the input rate the lower the output pulse duration, the greater the input pulse rate the greater the output pulse duration (0-100% going from 0 pulse per minute to 5000 pulse per minute, but having an amount of adjustment using a knob).

are these things that would be easy to build? It would seem so but I'm new to this and looking for new learning projects. any help would be greatly appreciated.

again, I'm new but have a basic understanding of ac/dc, capacitors, diodes, resistors etc...

 

[vne147]

I'm new to electronics and searching google I found this forum.

I am wanting to build a two part system that will have two out puts, one input.

the system is a 12v dc auto system
the input side will be a pulsed ground, up to 5000 pulses per minute.

from that i'd like to do these two things.

for one I'd like to have a knob that will adjust the system using a variable capacitor?
it will measure the pulse rate, and if the pulse rate is to high it will trip the output to ground.


the second I'd like to do is have the same basic setup, using a knob (again a variable capacitor?)
that would set the output. I want the system to take the pulsed ground signal and also send out a pulsed ground, but vary the output by the pulse duration (maintaining a constant pulse rate), the lower the input rate the lower the output pulse duration, the greater the input pulse rate the greater the output pulse duration (0-100% going from 0 pulse per minute to 5000 pulse per minute, but having an amount of adjustment using a knob).

are these things that would be easy to build? It would seem so but I'm new to this and looking for new learning projects. any help would be greatly appreciated.

again, I'm new but have a basic understanding of ac/dc, capacitors, diodes, resistors etc...

What is it you are trying to build? What is it supposed to do?

For the input, what is a pulsed ground? Do you mean the input should alternate between 12V and ground? What do you mean by "adjust the system"? Does it HAVE to be done with a variable capacitor? Does this knob set the threshold frequency above which the output will go to ground?

The second part makes a little more sense. "vary the output by the pulse duration (maintaining a constant pulse rate), " This is referred to as PWM (pulse width modulation). Does the knob for the second part set the input frequency that corresponds to 100%?

I think a little clarification would be helpful.

 

[joe_rocket]

the first part is going to trigger a light for the driver...
the second part is going to trigger a solenoid (theoretically).

beyond that though, let me address what is important...

For the input, what is a pulsed ground?
a pulsed ground, that is what I call it. the cars system is a negative ground, so a pulsed ground is just a negative pulse..

What do you mean by "adjust the system"? Does it HAVE to be done with a variable capacitor?
well, it should have some adjustability b/c not every condition will be the same, and this will allow fine tuning by the driver. It does not have to be a variable capacitor at all, just what I thought might work?

Does this knob set the threshold frequency above which the output will go to ground?
Yes.

Does the knob for the second part set the input frequency that corresponds to 100%?
yes.

I'm sorry I didn't make myself clearer, but it appears you have a pretty good idea of what I had in mind (I think).
-thanks

 

[vne147]

What is the source of the input pulse? I understand the input pulse frequency varies between 0 and 5 kHz but saying that it is a negative pulse still isn't saying very much. If you were to measure the voltage while the pulse is in its high state, what would it be? Also if you were to measure the voltage when the pulse was in it's low state what would it be?

 

[joe_rocket]

I do not know? searching around i found this:
RMS Voltage waves from the low tension (LT) side of the ignition coil

that is what it was called in another thread here. the positive side is 12v so I would assume that the ground would complete that 12v dc? in it's "low pulse" it would just be an open circuit, and when triggered it is a direct ground..

I did find this on a google search:
https://forums.off-road.com/jeepste...lub/83103-hei-tach-connection.html#post486843

The HEI module output is basicly a square wave 0 - 12 volts. But - it's nowhere near that, as it's driving an inductive load - with a secondary winding that's kicking back inductively. Another problem is it's wired as an auto transformer, the secondary low side is connected to the primary high side. Peak voltages are about 200 volts positive, and swinging to about - 150 in the primary.

 

[joe_rocket]

looking further i see this thread:
https://www.electro-tech-online.com/threads/pulse-generator.96574/

I think something like that is just what I need for the second part, but how would i trigger it?

I will continue to read and search, I hope somebody here can help me.

 

[rahul.sadtm]

looking further i see this thread:
https://www.electro-tech-online.com/threads/pulse-generator.96574/

I think something like that is just what I need for the second part, but how would i trigger it?

I will continue to read and search, I hope somebody here can help me.

if you need to build this type of pulse generator circuit, just use 555 timer in astable mode and keep the values of R and C according to your pulse timing. for more information of 555 timer IC you can go to this link-

**broken link removed**

 

[joe_rocket]

will this work?

 

[joe_rocket]

anybody have any input here please...

 

[shortbus=]

Have a look at this circuit; RMCybernetics - DIY Homemade Power Pulse Controller

Your solenoid would be connected to the mosfet.

Normally you don't switch/pulse the negative/ground connection.

 

[joe_rocket]

most all automotive systems do this, run +12v and pulse the ground.

at anyrate, looking at the link you left, it says vr1 and vr2 are used for changing the frequency and duty cycle, how will that work when I need to have them variable by the pulsed input?

 

[joe_rocket]

ok, thanks, I have that somewhat worked out, how about the #1 I asked about?

taking that pulsed ground? from what i understand this is the module:
https://www.electro-tech-online.com/custompdfs/2010/01/LM1815.pdf

i want to take the "reference pulse out"
and measure the rate, not the frequency. if the rate exceeds XXX then ground an output wire (rc timing)... is this possible? I saw in the Yenka program from a couple links back there are what they call "counters"....

 

[rahul.sadtm]

will this work?

well, your 555 timer is working in monostable mode, i think. where you have one stable and one unstable state. the unstable state is determined by your trigger pulse. So all the best and try this may be it works....

 

[joe_rocket]

it's not working, maybe I wasn't clear...


I will be needing a circuit that takes a variable frequency input square wave and if its acceleration rate is too great it needs to trigger an output wire.

ie, if it is 1khz to 3khz in 3 seconds do nothing BUT if its acceleration rate is 1khz to 3khz in 1 second trigger the output (preferable using a variable capacitor or resistor so it can be fine tuned)

can anybody do this, and if so how much?