Simple timing circuit

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kleenaccord45

Member - Posts: 8

Joined: May 14, 2002

Location: United States

Posted: May 14, 2002 at 10:29 AM / IP Logged

Anybody know how to get 7 sec. of +12volts from a constant source. A basic Timer circuit. I am thinking a capacitor or something of the sorts.

Big Dog

Gold - Posts: 1,265

This member consistently provides reliable information

Joined: May 02, 2002

Location: Quebec, Canada

Posted: May 14, 2002 at 12:01 PM / IP Logged

Hey KleenAccord,

A simple timer could be built using a relay and two 4700mfd polarized caps.

Go here https://www.the12volt.com/relays/page5.asp and look at constant to momentary. To lengthen the time replace the 1mfd with two 4700mfd polarized caps being careful to observe polarity. Should give you about 7 secs. Add another cap for extra time as needed.

Prepare your future. It wasn't the lack of stones that killed the stone age.

kleenaccord45

Member - Posts: 8

Joined: May 14, 2002

Location: United States

Posted: May 22, 2002 at 2:22 PM / IP Logged

I went to RadioShack and got a 4700M Farad cap.(5.99 about the same diameter as a quarter)

I wired as follows

87- went to +12 (AT THE BATTERY)

30- My output

85- went to the top of the cap and the of the resistor

the bottom of the cap and the other side of the resistor went to GND (AT THE BATTERY)

86- this was my trigger - I gave it +12 (AT THE BATTERY)

My output remained at 12.58 for several minutes -NOT SECONDS.

Where did I go Wrong?

I am thinking that the cap bought is way to big

the12volt

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Joined: March 07, 2002

Location: Louisiana, United States

Posted: May 22, 2002 at 2:25 PM / IP Logged

What size resistor did you use?

kleenaccord45

Member - Posts: 8

Joined: May 14, 2002

Location: United States

Posted: May 23, 2002 at 7:15 AM / IP Logged

10k

the12volt

Administrator - Posts: 3,955

Joined: March 07, 2002

Location: Louisiana, United States

Posted: May 23, 2002 at 8:19 AM / IP Logged

Hi Kleenaccord45, the values you've listed should be correct and it sounds like the resistor isn't bleeding off the charge of the cap and may be bad or have a poor connection. Double check the value of the resistor and your connections at the resistor and/or try another one.

the12volt

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Simple timing circuit

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