Interfacing mechanical relay with Spartan 3 FPGA

[rajnaren5]

Dear friends,
I want interface the mechanical relay with FPGA. Can any body help me. Please send me the circuit. I want use the following things: MCT2E, SL100 and IN4007. I am waiting for ur response.

thank u.
with
regards
raj

 

[Marcel Majoor]

So you want to use an optocoupler (MCT2E), a diode (1N4007) and a transistor (SL100 ?????? not sure what this is).
It seems you already have had some thoughts about it.
What is the problem then? I assume you did not pick these components just randomly?

Some general info: The FPGA uses a specific voltage, depending on the I/O bank used. Check what I/O pin you are using and then at what bank it resides and check it's voltage. Then you know what output level to expect. Then you need to interface this particular output to drive, for example, the optocoupler. You could use a logic-level mosfet to switch the optocoupler (or a 'mechanical relay' for that matter).

 

[sameh_yassin99]

Hello,
To change the positin of relay contact, you should apply a constant voltage across the inductor of the relay. Therefore you can connect the FPGA pin directly to one terminal of the coil while the other is grounded. this is pretty simple, why do we need a transistor and a diode?

We need the SL100 Transisto because.
The inductor will draw much current that may cause damage to the FPGA.
Therefore we apply the control signal to a the base(gate) of BJT(MOS) transistor so that the current will be drawn in the collector(drain) of the transistor.
Now, Why do we need a diode such as 1N4007?
When you remove the voltage from the inductor, it need some path to discharge the stored energy in it, so the diode creates that path untill the inductor discharges.



**broken link removed**

 

[rajnaren5]

Thank you my dear friend
i will apply ur suggestions