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  • Author Author: oldmanraskers
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CPLD Controlled Door Lock - Output Circuit

oldmanraskers

The weekend is over and I'm back to my design... I don't have much to say about the output circuit, except that I want to drive a bunch of 24V solenoids and provide an indication (via LEDs) when the output should be active. Below is the circuit I have come up with and hopefully there is nothing more to be done image Next I will be moving on to look at providing the CPLD with an external oscillator circuit and dealing with the JTAG connector image

 

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  • You should wire your LEDs so that the resistor is connected to 24Vand the LED cathode connected to OUTx - that way the LEDs will be on when there is power in the solenoids. The way your circuit is now the LEDs will come on when the output driver is off and will draw their current though the load. 560R will give you about 40mA though each LED when it's on and that seems like a lot - obviously it depends on how bright you want the LEDs but I'd be inclined to limit the power in the dropper resistor to 100mW max which would give you a max LED current of about 4mA and imply a series R of about 5k6, although I'd go for less current (about 2mA) and use 10k.

     

    MK