Status
Not open for further replies.

satchmolips

New Member
Hi,
I have set up a deterrent to try and stop fuel thefts. I have a normal 240V PIR motion sensor, which is live, then activates a blue strobe light and two small buzzers. In between the PIR and the strobe/buzzers is a AC/DC converter which takes voltage down to 12 volts. The strobe light uses 180 ma and the buzzers even less. All works well but my problem is that when the PIR switches off there is still enough residual current to activate the buzzers continually and make the stroble light flicker occasionally. Presumably this is because the PIR is always having a small output? What do I need to do? Put something between the PIR and the strobe/buzzers? Novice here so all help appreciated! Thanks in anticipation

Last edited:

forumlicker007

New Member
You could add a gain/sensitivity controlled driver between PIR out and strobe/buzzers.

satchmolips

New Member
Thanks, Can anyone point me at one of those on the web?
Would a resisitor of some kind do the trick also?

forumlicker007

New Member
You've to post a circuit or drawing about what you have right now.

satchmolips

New Member
Hi, this is my best attempt at a drawing

Attachments

• 17.9 KB Views: 77

forumlicker007

New Member
I assume the PIR activated output is 240V, which is then converted down to 12V and given to strobe and buzzer both are connected parallel. The PIR should have adjustment for activated and stay on time delay, photodiode sensitivity control etc. If these won't help you to solve, there must be a fault in the PIR assembly. Open and clean the circuit well.

satchmolips

New Member
Thanks,
Brand new PIR and sealed. Will perhaps try another unless any other suggestions?

forumlicker007

New Member
satchmolips, you've options are there. First measure the voltage output of 12v dc converter at residual session. Add a voltage dependent transistorized external strobe/buzzer driver. It should have a voltage sensitivity pot.

satchmolips

New Member
Hi,
I added a 60w light bulb in front of the AC/Dc transformer and this fixes it now. Thanks for all your help

mneary

New Member
Your PIR output device is probably a triac, so there's a snubber across it. It's likely to be of the order of 0.47 µF in series with about 220 ohms. You loaded the output so that the leakage doesn't trigger your load.

A triac feeding a transformer can be dangerous. It can trigger on half cycles, resulting in DC, damaging the transformer. Fortunately your 60W lamp also resolves this risk.

If you want to avoid this problem in future installations, use only PIRs that state that they can be used with fluorescent lamps. These have circuitry (usually a relay) that has little or no leakage.

tcmtech

Banned
Ever consider the so called "poisoning the well" method?

We had kids stealing fuel out of local farm equipment a few years ago.

One of the more clever local farmers left several fuel cans sitting by his farm equipment one night. Two were full and the others were empty.
The intention was to look like he had been fueling up but forgot the cans and had left them out.

They were the plastic jug type cans so this worked very well by the way. As it was explained to me he filled each one with about 4.5 gallons of E85 fuel and .5 gallons of muratic acid. (hydrochloric acid).
Hydrochloric acid reacts violently with the aluminum in the fuel system and the aluminum pistons and other engine components and the high ethonal content of E85 keeps the acid in suspension so it will stay mixed with the fuel for some time without the water and acid part settling out.

The next morning the cans were empty and one pickup and two cars were sitting along the road a few miles away. They each had puddles of fuel under them too from the fuel tanks corroding over night.

A little asking around later that week revealed that all three had the engines go out that night as well, and all within about a mile of each other.

The three owners were high school kids!

If you do the E85 and acid mixed with about half diesel I hear that it can destroy diesel engines too!

If you set it up right, I bet you will permanently stop the fuel theft and find out exactly who it is thats taking it!

Mikebits

Well-Known Member
Ever consider the so called "poisoning the well" method?

We had kids stealing fuel out of local farm equipment a few years ago.

One of the more clever local farmers left several fuel cans sitting by his farm equipment one night. Two were full and the others were empty.
The intention was to look like he had been fueling up but forgot the cans and had left them out.

They were the plastic jug type cans so this worked very well by the way. As it was explained to me he filled each one with about 4.5 gallons of E85 fuel and .5 gallons of muratic acid. (hydrochloric acid).
Hydrochloric acid reacts violently with the aluminum in the fuel system and the aluminum pistons and other engine components and the high ethonal content of E85 keeps the acid in suspension so it will stay mixed with the fuel for some time without the water and acid part settling out.

The next morning the cans were empty and one pickup and two cars were sitting along the road a few miles away. They each had puddles of fuel under them too from the fuel tanks corroding over night.

A little asking around later that week revealed that all three had the engines go out that night as well, and all within about a mile of each other.

The three owners were high school kids!

If you do the E85 and acid mixed with about half diesel I hear that it can destroy diesel engines too!

If you set it up right, I bet you will permanently stop the fuel theft and find out exactly who it is thats taking it!

That is the most irresponsible advice I have ever heard on this forum. HCL is very dangerous, someone could die, and I think such booby traps could land someone in jail on murder charges. This sort of thing is not legal at all.

Last edited:

SPDCHK

Member
So you are condoning theft?

What will the thieves do? Go to the police and say that people leave dangerous stuff out for them to steal? Dishonesty deserves punishment. Sorry, But I side with tcmtech on this. In South Africa crime has reached pandemic status. Police unable to do anything about it. People get killed for the equivalent of $5.00 (R50.00), and those murderers are still running free on the streets. Maybe in a country where the law of rule is still enforced I might agree with you, but here you have to take care of things yourself or you will be a victim of crime for the rest of your life. Mikebits Well-Known Member The US is not the Wild west frontier. Although I agree that we have a right to protect our property, we still must follow laws set by the lawmakers. Here in the US we have a right to defend ourselves with proper force to defend ourselves. If we use excessive force such as shooting a robber in the back as he flees the scene, then we are guilty of excessive force. Same token, Booby traps can kill and are considered excessive force since we are not in danger of being killed. Robbery does not justify possible murder. Video cameras might be a better approach. Suggesting to someone that they commit a crime is bad advice... Mikebits Well-Known Member So you are condoning theft? What will the thieves do? Go to the police and say that people leave dangerous stuff out for them to steal? Dishonesty deserves punishment. Sorry, But I side with tcmtech on this. In South Africa crime has reached pandemic status. Police unable to do anything about it. People get killed for the equivalent of$5.00 (R50.00), and those murderers are still running free on the streets.

Maybe in a country where the law of rule is still enforced I might agree with you, but here you have to take care of things yourself or you will be a victim of crime for the rest of your life.
I realize that in SA things are quite different than here in the U.S We still can count on our local police. I know SA is a different story, and you must defend yourself in anyway you can. TCMtech does not live in SA and is a U.S citizen, As far as I know, the US has not found itself in a position as SA, and we still have laws that we must follow, or we might find ourselves on the chain gang.

Last edited:

ghost3261

New Member
hey i need a 100w invertor (12dc-220ac)..
plz somone help me this project circuit...
automatic invertor...

thanx..

Mikebits

Well-Known Member
hey i need a 100w invertor (12dc-220ac)..
plz somone help me this project circuit...
automatic invertor...
thanx..

ghost3261

New Member
i want it quickly plzzz...

Mikebits

Well-Known Member
Last edited:
Status
Not open for further replies.