Thread: Millisecond Timer Circuit

How accurate does it need to be? There are plenty of circuits available online for the ubiquitous 555 timer, but if millisecond accuracy is your thing, you may want to be looking towards a microcontroller.

Not too accurate but still in the milliseconds area, it's so that the windows on my car to down/up just a tiny little bit when I open/close the doors. So really just a pulse

555 should do the trick.

Okay so I found a circuit, now the trigger pulse will be a constant voltage and I only need one output pulse when triggered

not sure if we understand each other, what i need is when the input gets voltage the circuit is closed for around 0.5s then opens the circuit and stays open

The trigger is the door sensor and it works by grounding out so when the door is open the trigger wire will always be les than 1/3 VS, I did come across something called an edge-trigger or something, basically there is a capicitor on the trigger wire and resistor to the VS wire so that it sees the change in voltage then goes back to normal state... I think

Or we can go real simple and ditch the 555 circuit and use a relay, a reverse relay and a DPDT relay and a few ground sensors like on the door sensor of the hood sensor from a car alarm

Originally Posted by BrownDog

Not too accurate but still in the milliseconds area, it's so that the windows on my car to down/up just a tiny little bit when I open/close the doors. So really just a pulse

I'm guessing that you want to relieve the pressure when you close the door, so when you open the door, the window goes down a few millimetres and once the door is closed the window closes up again.
I think Camaros came with that.

If that is what you want then you need to have 2 different one shot timers with 2 different outputs (one for the UP button and one for the DOWN button) triggered from the same door switch, The DOWN timer gets activated as soon as the door opens and the UP timer gets activated by the inverted signal of the trigger (Door Closed).

All you need is 2 555 (or a 556) and and inverter signal for the trigger (NPN transistor would do)

Originally Posted by ammlione

I'm guessing that you want to relieve the pressure when you close the door, so when you open the door, the window goes down a few millimetres and once the door is closed the window closes up again.
I think Camaros came with that.)

not really, my car has frameless windows and before i bout it was in a smash and now the body is somewhat twisted. when i close the door the windows dont go inside the seal properly that sorta just stick out and just lets water in, they go in if i put the window down just a little bit and put it back up.

worked out a real simple way without the use of 555 timers, gonna draw up a diagram and upload it

pretty crap diagram but my first one so its expected

when the door is open the switch grounds out so the first relay activates which in turn activates the second relay which winds the window down until the switch on the window grounds out. then when the door is closed the third relay activates which activates the fourth relay and winds the window up until the switch is no grounded.

i think it will work, will be a hell of a lot of adjusting :/

OOPS double post

get rid of the first two relays for a SPDT relay

Your original idea of a a pulse of .5 secs sounds better to me.
As I see it, you are driving the window motor by itself, instead of using the car motor driver. If this is the case, you won't be able to open the window when the door is shut (and you are driving).
Did the car had original electric windows or are you adding a motor to the mechanism?

Yeah it was better, however the trigger isn't a pulse it's just a voltage that's gets grounded out
Was going to splice the two wires on the the original ones
No all electrical windows from factory

Be careful if you go ahead with the relays, as you may put power back into the car's original motor driver and short it out to silicon heaven.

you should really connect the relays to the original up/down window buttons, its much safer to let the car controller deal with any overcurrents and such.

yeah i will, also gotta ad another switch and relay because if i leave like that and wind the window down the circuit will just wind it back up

2 of these will do what you want 1 in H mode and other in E mode
start across the door switch
output to window switch
you may need interlock between the 2 but the window switch/ motor should already be done
there maybe cheaper timers around but you need to find 1 with a start function