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digital output drive current help

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jllabs

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I have a controller that has an unusual digital I/O. When using its digital output - the drive current is only 220 uA @ 2.7 Vdc (yes micro amps), the output high state is 3.3Vdc no load and low state is <0.9 Vdc for each channel. I cannot find a SSR that will work with such a low drive current. Ultimately I want to control several 12 Vdc solenoids that need approximately 60mA each.

I do have a circuit diagram attached (power switching without relay) that I used on another system where the drive current was 1.5 mA @ 4.5Vdc, the output high was 5 Vdc and low was 0 Vdc. Can the initial resister value be lowered (substantially) to make it work for the lower drive current? Is there a SSR available that will work with such low drive current and output high?

I am not an electronics guy but can put most anything together with proper guidance. Thanks in advance for any assistance offered.
 

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jllabs

New Member
Additional info

I was able to try one of the two circuits and got it to work as shown in the attached sketch. The second circuit I was not able to test as I do not have the second transducer. I did build the circuit in LTspice and it works. However, the control is triggering at about 0.6 V and the control low is rated as <0.9 V. It could, in theory, not open or close unpredictably. The measured low is 0.0 V but this is without anything else connected to the controller.

Anyone's input would be appreciated...
 

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ericgibbs

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Most Helpful Member
I was able to try one of the two circuits and got it to work as shown in the attached sketch. The second circuit I was not able to test as I do not have the second transducer. I did build the circuit in LTspice and it works. However, the control is triggering at about 0.6 V and the control low is rated as <0.9 V. It could, in theory, not open or close unpredictably. The measured low is 0.0 V but this is without anything else connected to the controller.

Anyone's input would be appreciated...
hi,
For driving the relay, look at this pdf for the Si1012R/X, very low Vgate/source.
 

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ericgibbs

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hi,
For higher currents, look at this dual FDS6898AZ, using low Vgs.
 

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Last edited:

ericgibbs

Well-Known Member
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Can you provide a sketch or describe where the MOSFET would be used.
hi,
The Si1012 N MOSFET would replace the 2N2222 in your diagrams, change the value of the resistor to say 47R.

Post a drawing showing N MOSFET and we can check it for you.:)
 
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