PWM for semiconductor relais

Other Hardware Motors, Mechanics, Power and CNC
1

Hey everybody!

I'm playing with the Arduino Mega 2560 for some days and now i want to do my first real project with this little thing.

What I want to do is to control up to 10 semicondutcor relais with the Arduino PWM Outputs. Basically no problem, but each of these relais has an input current of at least 35mA. I read in the datasheet of the µC, that the total output current is 200mA, so I have to separate the µC outputs from the semicond. relais.
So my idea was to put a transistor between each pin pair (base resistance 2k2 + schottky diode base - collector if necessary). I would have preferred a direct connection (failure risk, project is prototyp for customer).

Now my question: Which transistor will you recommend for this task? Is a standard Tr. enough (standard PWM frequency of 490Hz)?

Thanks for you answers

2

If, by "semiconductor relays", you mean these proportional output solid-state relays, please know that you can't effect that variability through PWM.

Re. http://arduino.cc/forum/index.php/topic,94426.0.html
jimjam found that they require an actual analog voltage, not the mock-analog from the PWM (analogWrite) schtick. I think he derived the variable control voltage with the circuit provided by Grumpy_Mike in Reply #47 (Arduino Forum).