Connection of a diode

Vincenzo1309

Dear all,

What happens if I connected up the diode as seen in this picture attached?

As far as I am concerned, I have seen the transistor melting up...
But what exactly happens?

Kindly advise....

Mike Green

You are asking a lot of questions that are about basic electronics. You should read through some of the Wikipedia articles on basic electronics. Start with the articles on resistors, capacitors, inductors and then look at the article on diodes and the one on transistors. They're available in many languages.

Your question about the backwards diode has many possible answers depending on the specific values used in the circuit and the characteristics of the diode, the transistor and the resistance of the relay coil. In many cases, either the transistor or the diode will be damaged or destroyed. It's possible to choose components so a 9V battery used as the power source would be exhausted, but no other damage would occur.

erco

Your schematic shows an improperly connected flyback diode. The coils in solenoids and relays need flyback diodes (more later) for protection. But in the configuration you show, the transistor fried itself because the diode bypassed your coil, leaving the transistor short-circuiting your 9V battery contacts, which allowed too much current to flow through and overheat.

A proper flyback diode (installed in the opposite direction than shown) won't allow battery current to flow through. Its purpose is to absorb high-voltage transient spikes when the solenoid is turned off. Those can damage the stamp.

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Vincenzo1309

Hey erco,

Thanks alot for your explanation!