2 sec delay on reverse

Thread Starter

gerty

Joined Aug 30, 2007
1,302
I'm trying to figure out a simple 2 second or so delay for energizing a relay.
What I'm doing is starting a gear reduction (285 rpm) with a rf remote, the motor drives a pulley/cable for approx 10 seconds. When the cable reaches the right limit switch it stops, then reverses automatically.
I was counting on the gear reduction to act somewhat as a brake, now I think I need to add a small delay after the motor stops before reversing.
I don't want to get into adding a 555 or similliar circuit, but I may end up doing so.
Any suggestions?
 

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Wendy

Joined Mar 24, 2008
22,642
A simple resistor/capacitor may be all you need, depending on the relay coil. How much voltage, how much current?
 

Wendy

Joined Mar 24, 2008
22,642
The cap will be pretty large, but a simple RC charge will delay the relay. If you want slow on and fast off just add a diode. I think I have a illustration in my library, BRB.

********************************

OK, I misremembered, it was the other way around. I need to draw an example of what I'm talking about. You can also use a transistor to decrease the capacitor size.

Here is what I was remembering, the wrong schematic...



BRB, drawing.
 
Last edited:

Wendy

Joined Mar 24, 2008
22,642
OK, looking at it I think the transistor is necessary, though I could be wrong. A 555 would use a few more parts, but I think this would work. It's weakness is it needs a discharge resistor, preferably before R1.

 

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Thread Starter

gerty

Joined Aug 30, 2007
1,302
You da man!! Works perfectly. 2 seconds with these components
Values:
R1= 1.5k
C1= 220uf
Q1= pn2222
CR1= 1n4001
Relay I tested it on was 180Ω @12vdc
Thanks
 
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