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newbie, relays, transistors.

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waltonlobot

New Member
Okay, apologies for the dumb questions.. enthusiastic but unscientific newbie.

I bought a 12v relay kit and assembled it, (the Kemo, B197), hoping to trigger a motor when an led is triggered by a 555 timer. no luck.

1. Im sure I tried 12v, but 9v was easier.. Would a 12v relay need to be powered by the full 12v ? (relay is 1xON 6/3 amp)

2. The negative of the relay circuit appears to go somewhere else, would this be the negative of the "motor circuit" or the negative of the 555 circuit?

3. This still requires power to the motor right? And the relay circuit simply acts as a mechanical switcher.. Would I hear it switch if that bit was working? Is it because the motor needs too much torque to start up, its just a tiny hobby type motor? Is it because the led's flash kinda fast?

4. Okay, what I really just want to do is build a mechanical drum machine, where 555 timers trigger toy motors that hit things... trying to find the answer here I get the impression just a transistor could do this? I dont care about blowing the whole thing up, and, it will all be 9v DC if I can possibly help it.

Thanks so much for any help, the instructions on the kit were very poor, and Im really still just at the stage of copying simple circuits and trying to get a clue what they do... Lots of possible combinations even with a few components when you are a moron! :)
 

stevez

Active Member
I am not sure I understand the questions but I'll try offering some bits of info.

A. A relay is a switch - contacts open or close to control the flow of electricity. Power applied to the coil moves the contact(s) between on/off.

B. The coil that moves the contacts requires some power - how much depends on the design of the relay. The source of power that you are using to open/close the relay might or might not have sufficient voltage/current - or as you suggest, the power might not be on long enough.

C. Some relays will operate with significantly less voltage than design - some will not. Experimentation or getting more info on relay will answer that question.

D. Lots of relays make a click when they operate. Some are quieter than others and you may not hear it because of ambient noise.
 

bogdanfirst

New Member
there is something about relays. you can buy the same type of relay, 5 of them, but each will operate at a certain voltage. i bought 12V relays, and some were working fine with 6-7V, but others required 11.5V to function.
there is also another thing about relays. they have hysteriesis(if i am not confusing the term),that means that you need a highter voltage to make the coil moove the contacts, then you need to maintain the contact. this is due to some factors about the electromagnetic field generated by the coil.
 

waltonlobot

New Member
thanks for your replies, Im still confused of course, but it helps.

to clarify the most basic of questions though so I can test the relay with voltages.

the circuit has a positive and negative to connect the power from, in the diagram it appears this negative "might" connect to either the motor, which I want to drive, or the circuit which is the trigger for the relay. Is either of these correct?

there are two other leads, one marked "relay" the other not that also come out of the circuit, so, all I do is hook up my motor circuit so that the positive is disconnected from the power but "joined" by the relay circuit, with one wire of the relay connect directly to the battery positive, and the other connected to the motor positive, right?

Sorry for my confusing explanations, I appreciate the input.

Im wondering now if I just start by using good old fashioned mechanical bell type devices, could I drive these with just a transistor? they would sound great too! :)
 

bogdanfirst

New Member
how about posting the circuit? maybe this way we can help you better....
about driving with transistors, .....i dont know what so say, if they are low current and low voltage you can drive them with a transistor.
 

waltonlobot

New Member
thanks guys...

Ill do some schooling up on generally how relays work and stuff and just try to get it to work ONCE before I bug you more.

I could scan the circuit, but seriously, its a relay, two resistors and a transistor....

I think you are trying to help with a harder question than I am asking..

but, anyway, Ill go read some more (I have the famous forest mimms intro to electronics, but its not terribly helpful on the relay thing)

thanks again.
walton.
 

waltonlobot

New Member



okay, I give up, here is the circuit, Im wondering whether I broke the transistor...

But, so, just to get anything to work off the relay, motor or led whichever is easier for me to get it tested..

in lead goes to the 555 timer circuit. positive and negative go to the battery terminals, relay acts as a switch between the positive of the battery for the "driven" circuit, the motor I want to turn on, or an led just to test it.. now, in the picture of the circuit, but not really the diagram here, it appears the negative of the relay should be going somewhere else as well?

or, given this circuit, is it simply, power the relay with 12v, connect the in to the led that is flashing on the timer circuit, the switch acts as a switch, so, it doesnt really matter where it breaks the circuit for the device you want to trigger... and, no negative leads are shared between different circuits and Im crazy....

thanks for all the help again! [/img]
 
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