PIR operating a relay

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Barmybaz

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Help please,
I have several projects that I wish to run from a pir at 6volt, as the projects all tend to run at different voltages I thought operating a relay would be the easiest option, I have available several,
SKU023606 Pirs
BC547 transistors
JQC-3F(T73) relays 3volt, coil resistance of 28Ω (i think)
Various, resisters, Diodes and bits,
Do I have enough bits? do I need more? how do I put them together?
 
hi,
Use your BC547 as a relay driver.
If the PIR output goes high on detect, say ~5V, the use a series resistor to the Base of the BC547.
Add a diode across the relay coil.
E
 
ericgibbs said:
hi,
Use your BC547 as a relay driver.
If the PIR output goes high on detect, say ~5V, the use a series resistor to the Base of the BC547.
Add a diode across the relay coil.
E
Click to expand...

I just spoke to the OP and learned he used to be an assembler. I think he could work from a schematic but may not be able to get how things work together?

Barmybaz, sorry I didn't mean to be "rude" when I changed the subject in "Chat" I don't have much time today and needed a Math question answered.

Good luck with your project. Eric, will get you straightened out.

kv
 
Hi
thanks for your advice, kv is right about a schematic, just to be sure, is this the circuit you are suggesting,
Its just that I'm a pensioner looking for a hobby, not very good yet.
no prob' kv
 

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Barmybaz said:
Hi
thanks for your advice, kv is right about a schematic, just to be sure, is this the circuit you are suggesting,
Its just that I'm a pensioner looking for a hobby, not very good yet.
no prob' kv
Click to expand...

As he suggested you'll need a resistor on the base of the Transistor; not to sure what the value would be. The Diode looks correct.

kv

Edit: I spotted a 10k on the base of several circuits using a uC. Which most likely is between 2 and 5v. Should work; but then I'm not an Engineer.
 
Last edited:
hi Barmy,
Post details of the PIR output signal, ie: Low /High voltage and type number if you have it.
E
 
Hi Eric
The output of the p,i,r is quoted at 3v.
going to put it together today, (what could possibly go wrong, lol)
 
Eventually got to wire it up today, BRILLIANT ! EXCELLENT !
Now my cat repellent, (solar powered). grandchildrens fairy house, (night light) and light house (garden light) are all a reality.
can't thank you both enough for your help.
One point, I had to take out the diode, (one I found in box of bits, could have been faulty) does this matter, if so can you suggest a replacment,
Thank you both again.

Barmy
 
One point, I had to take out the diode,
Click to expand...
Hi,
A suppression diode across the relay coil is essential, cathode to supply voltage, anode to transistor collector.
E
 
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