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reciever circuit not working

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D.J.

New Member
Hi,

I am a new memner of this site.

On Tony's Site, he has an RF reciever "Simplest R/C Circuit" and I can't get it to work or even understand it.

I don't have any SCR's so I used an NPN transitor in its place. I also ran the circuit off Five volts. The transmitter circuit was the "Simplest RF transmitter".

Where does the the SCR gett it's positve from, both ends of the coil are hooked up to negative.

I had this circuit working before but now that I try it again, with new parts, it won't work at all.

Tony's Site adress is:
**broken link removed**
Great site!!!

Help is appreciated,

Regards,

D.J.
 
They are talking about current in the order of 30uA coming out of the tank circuit and switching the SCR, i doubt you'd find a transistor that could do the same thing. Rather than change the components and modify everything why not go down and get an SCR? it may be an idea to Google SCR and find out what one is and what it does.
 
D.J. said:
Hi,

I am a new memner of this site.

On Tony's Site, he has an RF reciever "Simplest R/C Circuit" and I can't get it to work or even understand it.

I don't have any SCR's so I used an NPN transitor in its place. I also ran the circuit off Five volts. The transmitter circuit was the "Simplest RF transmitter".

This is rather like saying "I've built a bicycle, but I didn't have any wheels, so I used planks! - why won't it work?".

An SCR and a transistor are totally different devices, you can't replace the SCR with a transistor and expect it to work.

Bear in mind as well, the SCR specified is a special high sensitivity one, so you need to make sure you use one that's very sensitive, details are given on the webpage!.

The DC supply is only needed to match the relay used, if you have a 5V relay a 5V supply would be fine.

Where does the the SCR gett it's positve from, both ends of the coil are hooked up to negative.

The 'coil' is a tuned circuit, with a variable capacitor across it for alignment. When it receives a strong signal on the correct frequency the signal is transformed down by the tap, and the resulting higher current is fed to the gate of the SCR. It doesn't matter that it's AC, the SCR will only respond to the positive half cycle (effectively rectifying it), and turn the SCR ON. A function of an SCR is that they latch ON once switched ON, so a short pulse latches it and closes the relay.

It's a particularly crude circuit, but that's what it's supposed to be! - as simple as it can be!.
 
Reciever not working

Hi,

Thanks for the quick response, I think I understand.

I read about SCR before I made the changes and it looked resonable. I had no need for the relay to stay on, I just wanted it to come on when the transmitter was activated. And since the transmitter was using a transitor, I wanted the recievr to also.

So you are saying that the SCR is their so it can detect the slitist change in currrent. But since the coil was already negative I would need a very strong signal to change the polarity right?

Sorry if these are some stupid questions, I'm fourteen and just got into electronics, so bear with me!

Thanks,

D.J.
 
Re: Reciever not working

D.J. said:
Hi,

Thanks for the quick response, I think I understand.

I read about SCR before I made the changes and it looked resonable. I had no need for the relay to stay on, I just wanted it to come on when the transmitter was activated. And since the transmitter was using a transitor, I wanted the recievr to also.

So you are saying that the SCR is their so it can detect the slitist change in currrent. But since the coil was already negative I would need a very strong signal to change the polarity right?

Sorry if these are some stupid questions, I'm fourteen and just got into electronics, so bear with me!

My daughter is 14 as well!.

A transistor won't switch like an SCR - as soon as an SCR is triggered it latches ON, and that's the end of it. With a transistor, assuming there's enough current to turn it ON, it won't just switch ON - it will rapidly turn ON and OFF at the carrier frequency, you would need more components to prevent that happening.
 
reciever not working

Hi

I don't want to get an SCR becuase I have to order it online and shipping takes a week. So what do I have to do to make this circuit work with a transitor.

Or do you know of another simple reciever that uses a transitor. It doesn't have to be tuned, cause I could chnge the frequency myself to match the transmitter's.

Thanks again this is very helpful!

D.J.
 
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