Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Is there such a thing, if so what's it called?

Status
Not open for further replies.

TCLynx

New Member
Is there some sort of circuit or switch that would send a .2 second (aprox) positive pulse when power is applied.......
And then send a .2 second (aprox) negative pulse when power is removed?

I realize the negative pulse when power is removed might not be possible so alternatively.
Is there something that would send a .2 second positive pulse when power is applied and then some duration later (between 10 minutes and 30 minutes) send a .2 second negative pulse?

What would such a thing be called if it does exist so I can go searching for it?
 

crutschow

Well-Known Member
Most Helpful Member
By negative pulse, do you mean the signal is setting at some positive voltage and then momentarily goes to zero volts?

For the 0.2s requirements you could use a 555 timer configured as a one-shot.

For the longer time period you could use an oscillator (555 configured as an oscillator) and a counter such as a CD4060.

To learn about these devices just Google.
 

TCLynx

New Member
By negative pulse, do you mean the signal is setting at some positive voltage and then momentarily goes to zero volts?

No, I mean just send a brief positive pulse at the start and then a negative pulse as in switch the wires like with an H-bridge or something.

It is a car door actuator that I am trying to control here. Takes a .2 second 12 vdc pulse one way to actuate it one way then a reversed pulse to have it go the other way.
 

MikeMl

Well-Known Member
Most Helpful Member
A capacitor? What is the resistance of the actuator?
 

Attachments

  • Pulser.gif
    Pulser.gif
    37.9 KB · Views: 97
Last edited:

MikeMl

Well-Known Member
Most Helpful Member
According to my cheap multi-meter, between 2 and 3 ohms

That would take a huge capacitor. RC = 0.2, R=3 therefore C=0.07F or 70,000uF.
 

MikeMl

Well-Known Member
Most Helpful Member
It is simple, if you have room for a 70,000uF 3lb electrolytic capacitor :D
 
Last edited:

TCLynx

New Member
Space isn't a huge issue for this situation but I don't think I want to spend too much money for just a capacitor.
 

bountyhunter

Well-Known Member
I realize the negative pulse when power is removed might not be possible
It's easy. Create an "internal rail" fed through a diode from your positive power rail to a electrolytic cap. As power goes down, the primary rail drops. Use a comparator to detect when the primary rail is below the "internal" rail across the cap which powers the comparator. Use the comparator to fire a 555 one-shot and make a pulse as the prime rail is going down.

Here's an example. The PNP's bases are turned on by the 5.1k resistor as the 12V rail falls and the cap's voltage holds up for a while.
 

Attachments

  • turn off.jpg
    turn off.jpg
    15.4 KB · Views: 89
Last edited:

TCLynx

New Member
So...
I could create a circuit that has a 555 timer hooked up as a regular one shot timer that would give a positive pulse. And also have an internal rail as you describe that would fire a second one shot 555 timer wired to produce a negative pulse? Then I just need to work out how to make sure I'm not causing anything funky to back feed into the wrong parts of the circuit.

Cool Time to look up some stuff and see if I have the parts on hand to do anything with what I find.:)
 

crutschow

Well-Known Member
Most Helpful Member
If you want to generate a pulse in either direction for the solenoid, then you will need to drive it with some sort of bridge circuit. But you will need some source of power for the negative pulse when the rest of the power is removed.
 
Status
Not open for further replies.

EE World Online Articles

Loading
Top