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Help with 12v relay and transistor

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Your living up to your avatar name there, Uncle $crooge :p

Fine... Open = On and Close = Off

But anyway u want to say it, the thing just doesnt want to work!

David
Hee, hee.:rolleyes:
You speaky zee backwards.
Maybe English is not your main language:
1) An open contact does not conduct. It is turned off, not turned on.
2) A closed contact conducts and is turned on.
See?
 
Yes i see. But i really wish i saw my board working.... :)

David
We speaky zee English here.
Other sites speaky zee Chinese or Korean.
Electronics is simple if you speaky zee the correct language.
 
Check if the relay is working without the load. The trigger signal comes from the Atmega pin; you may want to try to have a pulldown resistor.
 
I went over to my college yesterday afternoon to get some help from a electronics professor. It seems the transistor i was using wasn't the correct type? Therefore, they suggested i use a MOSFET transistor (2n5457).

After an hour or so, we got it to click the 12v relay. However, it does not seem to be working correctly (oh course, after i brought it home). You can barely hear the relay trigger and once i take away the 5v, it seems to stay triggered. Aside from that, its not producing 12v out so it seems its not triggering it all the way (hints maybe the faint clicking) When i hooked it up straight to the 12v on one side and 5v on the other, you can hear (and feel) it switching closed.

Not sure whats going on but im open to hearing your suggestions :)

David
 
A 2N5457 is not a Mosfet. It is a jFET.
Its max conduction is from 1mA to 5mA which is too low to turn on a relay.
We have no idea how you connected its pins.

EDIT: Its gate must have a negative voltage to turn it off.
 
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Alright, since the jFET did not work (it clicked nicly when i replaced the 1k resistor with a 220ohms) but it seem to over-heat the transistor and now its pOOp. And it also seems i can not get the Small Signal Transistors NPN 30V 100mA HFE/8 (BC548CTA) to work at all. So where too now?

What in this list here [RadioShack.com] would i be able to get in order to get this thing working????

David
 
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The relay circuit should work as it is drawn in your schematic. Therefore, there is something wrong with the parts or the construction. The BR transistor you show is not proper, as the relay needs over 100 mA and the BR transistor is rated for 100 ma absolute max. Your relay part number indicates a non built-in diode type, but the relay may be erroneously supplied with a built-in diode. I would check the relay coil to see it has exactly the same resistance (but appox 100 ohms) with the ohmmeter leads connected in both polarities. If it has a diode, proper polarity must be observed. Try a 2n2222A transistor, which Radio Shack most likely has. Check your 1n4001 diode with an ohmmeter as well. Check your resistors with an ohmmeter. Check and double check your connections Check your 12V power and make sure it is DC with proper polarity and voltage applied. If all the parts are good and the connections are correct, it has to work.
 
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