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I need to control an old projector that doesn't have an auto turn on on power. I thought of making a 555 timer circuit I saw on the internet.

enter image description here

It turns the LED (in this case it would be my relay) on after a certain time, and it stays on.

I need it to stay off for 10 seconds after power and then turn the LED/relay on, wait another 2 seconds and turn the LED/relay off and stay this way.

The relay will work as a button switcher connected to the power button of the projector.

Can anyone help me solve this? I have some knowledge of electronics, but not at this level I guess.

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1 Answer 1

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Since you need two timing periods you would need two 555 timers.

Here's an answer that is very similar to what you're asking for, you would just need to adjust the on time from 1 second to 2 seconds, you would do that by increasing R7.

To have it trigger on power up you can use a resistor and cap on the trigger pin of the first 555 (replacing V2) as shown here. Just use R1 and C1. R2, C2 and the switch are for retriggering it, so you can leave them out of you don't need to do that.

Here's an updated circuit that is simpler and includes power on startup. delay circuit delay circuit output

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  • \$\begingroup\$ That was so great and fast...I really appreciate it. I'll try that to see if it works for me. Anyway, I'm really happy with your answer. Thanks a lot. \$\endgroup\$ Oct 25, 2022 at 5:48
  • \$\begingroup\$ @ClaudioSouza Note that the timing depends somewhat on the supply voltage and transistors used for the current sources, you might have to play around with R3 and R7 to get the timing right. R3 is the delay before turn on, R7 is the on time. R2 affects the timing of both. At 5V you will need to double the size of the timing caps C2 and C3. \$\endgroup\$
    – GodJihyo
    Oct 25, 2022 at 5:54
  • \$\begingroup\$ @ClaudioSouza I've added an updated circuit, it's a bit simpler as I've removed the current sources (they were just so smaller caps could be used) and the timing will now only depend on the timing resistor and cap values. \$\endgroup\$
    – GodJihyo
    Oct 25, 2022 at 6:29
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    \$\begingroup\$ A 556 is two 555s in one package, so could be a bit tidier and more compact \$\endgroup\$
    – Chris H
    Oct 25, 2022 at 13:58

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