Voltage Stepdown

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  #1  
Old 09-16-18, 02:07 PM
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Voltage Stepdown

Hi, I have a PIR motion sensor that switches a light on in my garage. I would like to use a signal from this to send a signal to my home automation system via the gpio on a sonoff switch (with esp8266).
So far I have only been able to find the swiching signal at the relay. Unfortunately this is around 22v and I need either 3.3v or 5v.
I guess I can step down the voltage using resistors but I imagine this is not a good idea for heat and efficiency reasons.
can anybody suggest a more professional approach please?
 
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Old 09-16-18, 02:25 PM
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Welcome to the forums.

If that is a 120vAC motion sensor and does not contain a transformer...... you must use a relay to isolate your circuit from that 120vAC. You can use a low current 24vdc relay tied across the existing one.
 
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Old 09-17-18, 04:29 AM
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Relay spec?

Thanks PJmax
I did think of that but I was worried that the current taken by the additional relay may be too much for the PIR circuit board. Is there a particular spec I need to look for?
 
  #4  
Old 09-17-18, 05:05 AM
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Relay Spec?

something like this??
https://www.amazon.co.uk/Relpol-RSM8...v+signal+relay
 
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Old 09-17-18, 04:47 PM
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There should be no problem driving two relays. Your linked relay is fine.
 
  #6  
Old 09-18-18, 12:46 PM
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Solved

Thank you again for your help
 
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