Build a Radar detector screamer for under $10

[Jantar]

Is this still working fine for you? Have you made any improvements since the initial model? I've got to set up a screamer over the next couple of days so I'll give this one a go. Not really to keen to pay $175 for a screamer from radardirect.

Yes, its still working perfectly. I did find one issue when I changed from a GS1200ss to the VStrom. Make sure that it is mounted out of the air flow, otherwise it will detect fog, pollen, fine dust etc as smoke and give a false alarm.

Just been down to dick smith in search of parts. They didn't have the right resistor (the closest was a 3.6k 0.6W) but I noticed they had this car reversing beeper. http://www.dse.co.nz/cgi-bin/dse.sto...uct/View/L7060

Would this work as a screamer without having to use a smoke alarm?

It probably would, but you would still need to find a method of triggering it from the radar detector. The earplug output would not be suffient on its own and may damage the detector.

[MrMelon]

Sweet, off to jaycar in the morning to get the necessary bits then. Where's the best place to take the feed for the radar detector power too?

Cheers

[MrMelon]

The smallest 3k3 resistor I could get at jaycar or dick smith was 0.5W. Will this harm the detector in any way?

[k14]

It shouldn't. iirc, that is the max power it can dissapate. So having one over rated for the job shouldn't cause any issues.

[MrMelon]

Well I made a cable up with the 3k3 0.5w resistor inline with the middle pin but I can't get the detector to set the smoke alarm off properly. When it's plugged into the headphone jack and I connect the wires to both sides of the test switch on the smoke alarm it'll set the smoke alarm off constantly when the wires are one way around, and not at all when they're reversed. The detector powering on doesn't set it off.

Any ideas? Does it make a difference where the volume is set on the detector? It's an escort passport 8500.

[Jantar]

I'm using a passport X50, it it seems to work fine. If the wires are the wrong way around it wont work at all, but the correct way it only works when the detector is sending a signal.

You may be using a different model smoke detector to the one I'm using, so here's something to try. With the radar detector disconected just short out the pins on the detector and see if it screams. If it does then you have one that doesn't need a signal, just a short. In this case you will need a diode as well to prevent a back feed from the smoke detector through the radar detector.

Try using an electronic multimeter to see what current is required to set it off, you may need to change the value of the resistor to suit.

[MrMelon]

Yeah I got this detector from dick smith so it might be a different model. It goes off when the test pins are shorted. Where would the diode need to go? Should I use any one in particular?

My freaking multimeter's in a box somewhere in storage at the moment so I can't do any proper testing.

Do you know what brand your smoke alarm was? I might head off to the warehouse tomorrow and see if I can find one if it'd be easier.

[Jantar]

Ok, The fact that the smoke detector goes off when the pins are shorted tells us that there is a voltage across the test pins. You need to determine which is positive and which is negative, then insert a diode to block the current flow. There is a risk that doing this may also block the signal from the radar detector.

I'm not sure of your level of electronics knowledge, but if I was doing this with a detector that required a direct short across the test pins to activate, then I'd be more inclide to use a switching transistor with the emitter and collector across the test pins and the Base and emitter leading back to the radar detector. The 3k3 resistor would be between the collector and the smoke detector, and another 3k3 resistor between the base and the radar detector. I would also put a 47pF capacitor in parrallell with the transistor between the base and the emitter.

I guess I was lucky in finding one from the Warehouse that required a volage rather than just a completed circuit.

[StoneChucker]

Since I haven't read all of the main post, or the replies, please excuse if I am repeating something...

Be careful while opening up the smioke detector! There are a couple of types and one (maybe all, can't remember) has a radioactive compound between two metal plates (again, I think it's between plates). From memory, the most common type uses a small amount of radiation from the tiny source between the plates to detect smoke. It does this by a method which I do know, but for the moment can't remember.

What I do remember, is the the info I had said never to expose the radioactive material, as there is a chance of ingesting it (breathed in or via hands), which would prove dangerous at best, fatal at worst. Obviously it's safe when in the unit, and even safe to be next to the unit, but not when taken apart. (btw, I don't mean it's dangerous to open them up, it's not. I'm specifically referring to the radioactive component within.)

Dave.

[kevie]

what Id like to make is a little unit that will activate the radar detectors hahhaha will slow you buggers down thinking its a cop nearby eh

[Lou Girardin]

what Id like to make is a little unit that will activate the radar detectors hahhaha will slow you buggers down thinking its a cop nearby eh

Jaycar sell them. Might be K band though, so it won't work on good detectors.

[k14]

Since I haven't read all of the main post, or the replies, please excuse if I am repeating something...

Be careful while opening up the smioke detector! There are a couple of types and one (maybe all, can't remember) has a radioactive compound between two metal plates (again, I think it's between plates). From memory, the most common type uses a small amount of radiation from the tiny source between the plates to detect smoke. It does this by a method which I do know, but for the moment can't remember.

What I do remember, is the the info I had said never to expose the radioactive material, as there is a chance of ingesting it (breathed in or via hands), which would prove dangerous at best, fatal at worst. Obviously it's safe when in the unit, and even safe to be next to the unit, but not when taken apart. (btw, I don't mean it's dangerous to open them up, it's not. I'm specifically referring to the radioactive component within.)

Dave.

Dont worry. All they are using is the speaker part. Removing the smoke detector bit (the bit with the radioactive material in it) and instead using the radar detector to trigger the sound buzzer.

The way it works is that one side has the radioactive substance emitting alpha rays at a fairly high rate towards a detector. So long as the detector keeps sensing the rays its fine. If however smoke gets between the source and detector then the buzzer will go off. Pretty simple really. Alpha rays are very weak and normally don't even penetrate a piece of paper. Just being around the substance is also not of any consequence, it is hazardous if you ingest it however. Will be very bad indeed.

[Jantar]

Just being around the substance is also not of any consequence, it is hazardous if you ingest it however. Will be very bad indeed.

Quite correct, and that is why I wasn't prepared to open the ionization chamber to see what type of triggering circuit it used.

[Steam]

Hey can you guys please save the ionisation chamber bit for me, I'm collecting Americium. I need about 80kgs of it, it's going to take a while to collect but it's my only option as you need a license to get Uranium 235.
Thanks!

[k14]

Hey can you guys please save the ionisation chamber bit for me, I'm collecting Americium. I need about 80kgs of it, it's going to take a while to collect but it's my only option as you need a license to get Uranium 235.
Thanks!

Just enroll as a physics student at a uni, they have access to heaps. Will take a while to get 80kg of it. Maybe go and ask the iranians?