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Current into Digital Output on ADC-11

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Current into Digital Output on ADC-11

Postby DougOffin » Fri Nov 07, 2008 6:06 pm


Is it possible to use the digital output on an ADC-11 as a current sink? I would like to control a relay with the digital output. First I tried connectng the low side of the relay to ground and the other to the digital output so that when the output was high the relay activated. This didn't work, which I assumed was because the Picologger can't supply enough current for the relay..

After this I tried connecting a 3 volt power supply to the high side of the relay and the digital output to the low side so that when the digital output was low the relay activated. This worked but I am concerned I might damage the Picologger. The current is <5 mA. Any advice would be great,


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Postby PeterF » Wed Nov 12, 2008 12:24 pm

Hi Doug,
The digital output of the ADC-11 is very low power, maybe 3.3 volts at 1mA output. It certainly cannot drive a relay, either pull-up or pull down. You will need to have a buffer stage. The simplest would be a logic level FET or a logic level relay driver. Don't forget to use a parallel diode across the relay coil to protect the FET. A relay driver should already have protection.
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