12volt to 6 volt adapter for PIR unit (anti horse thief) - Electronic Circuits Projects Diagrams Free

petermanndorset · 1st November 2003, 04:06 PM

HELP? We were robbed recently of everything (£1700) from our Stable tack room deep in the Dorset countryside in the UK. Some one has given me a PIR unit, which runs from 6 volts. I want to use it from a 12 car battery and using a relay supply power to any anti thief device I fancy…i.e. a car spotlight. I know nothing about electronics but can use a soldering iron. My question is How to I reduce the 12 volts down to 6 volts so that the PIR unit does not blow up? I know a resistor should be used but have no idea how to work out which one to get.The PIR unit does not have any written data with it. Sorry to sound so dumb but I have to start somewhere. Peter

crust · 1st November 2003, 05:26 PM

Depending on the current draw, you could use a 7806 regulator. Then use your relay to switch a 12V lamp. Is there no AC power in the area? If there is, you can buy the whole integrated unit with dual floodlights and the pir sensor for about $50US, so maybe 30 to 40 in your currency.

Roff · 2nd November 2003, 05:26 AM

I'm attaching a schematic that might work for you. I picked an LM317 for the regulator because Maplin doesn't seem to have the LM7806, but I don't know what your resources are. If you select a different relay, it needs to handle 10 amps of contact current and the coil should draw less than 100ma at 12v. The 12 AWG refers to the minimum wire size you need for the wire that interconnects the battery, the relay contacts, and the spotlight. The size of the rest of the wires is not critical.

petermanndorset · 4th November 2003, 07:18 AM

'm attaching a schematic that might work for you. I picked an LM317 for the regulator because Maplin doesn't seem to have the LM7806, but I don't know what your resources are. If you select a different relay, it needs to handle 10 amps of contact current and the coil should draw less than 100ma at 12v. The 12 AWG refers to the minimum wire size you need for the wire that interconnects the battery, the relay contacts, and the spotlight. The size of the rest of the wires is not critica

Many thanks
peter :wink:

Roff · 4th November 2003, 07:26 PM

Peter, go back and look at the schematic I posted. There was an error and an omission, both of which I have corrected.

1Steveo · 27th October 2007, 04:18 PM

Pettermann,
I would use the PIR to trigger a camera.

1st November 2003, 04:06 PM	(permalink)
petermanndorset New Member	12volt to 6 volt adapter for PIR unit (anti horse thief) HELP? We were robbed recently of everything (£1700) from our Stable tack room deep in the Dorset countryside in the UK. Some one has given me a PIR unit, which runs from 6 volts. I want to use it from a 12 car battery and using a relay supply power to any anti thief device I fancy…i.e. a car spotlight. I know nothing about electronics but can use a soldering iron. My question is How to I reduce the 12 volts down to 6 volts so that the PIR unit does not blow up? I know a resistor should be used but have no idea how to work out which one to get.The PIR unit does not have any written data with it. Sorry to sound so dumb but I have to start somewhere. Peter

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1st November 2003, 05:26 PM	(permalink)
crust Experienced Member	Depending on the current draw, you could use a 7806 regulator. Then use your relay to switch a 12V lamp. Is there no AC power in the area? If there is, you can buy the whole integrated unit with dual floodlights and the pir sensor for about $50US, so maybe 30 to 40 in your currency.

4th November 2003, 07:18 AM	(permalink)
petermanndorset New Member	'm attaching a schematic that might work for you. I picked an LM317 for the regulator because Maplin doesn't seem to have the LM7806, but I don't know what your resources are. If you select a different relay, it needs to handle 10 amps of contact current and the coil should draw less than 100ma at 12v. The 12 AWG refers to the minimum wire size you need for the wire that interconnects the battery, the relay contacts, and the spotlight. The size of the rest of the wires is not critica Many thanks peter :wink:

4th November 2003, 07:26 PM	(permalink)
Roff Experienced Member	Peter, go back and look at the schematic I posted. There was an error and an omission, both of which I have corrected.

27th October 2007, 04:18 PM	(permalink)
1Steveo Experienced Member	Pettermann, I would use the PIR to trigger a camera.