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Hoping to upgrade a transistor. 3
I don’t trust myself to pick one and don’t have the time to experiment, so I thought I’d ask here. A guy designed this for me and while I can assemble boards, my electronics knowledge is lacking.
This circuit fires a solenoid. I have gotten reports from testing that this transistor doesn’t seem to have the same power as the ones we used on a pervious design.
The current transistor is fairly weak and won’t trigger some of the larger solenoids that our old design would.
I was hoping that there would be a drop in part that I could just switch to easily.
The part I’m currently using is.
NDS355AN N-channel Enhancement Mode Field-effect Transistor Q1 SOT-23Ax 2N7002
Could anyone help and give me some advice or possibly pay numbers to try?
I think the hangup is the amount of current the device can pass. Get the data sheet on the device, then go hunting for something with more “oomph” in the same package. Be open to the _possibility_ of needing a heatsink.
EDIT: just looked it up – N-Channel Enhancement Mode Field Effect Transistor 60V, 0.115A, 7.5Ω.
See if you can find something with lower resistance, or higher current – a bit over a tenth of an amp isn’t a whole lot. Might want to think about a different package, too; sot-23 is going to have pretty limited options.
Try looking up AO3400A. Should be more capable.
BTW, what is your VCC level? Is it more than 5v? If that is the case you need a P-MOS controller by another N-MOS else it will fry your chip.
If I read your schematic correctly, the solenoids are fed with the voltage provided by your on-board regulator (REG1117-5).
That regulator can at most deliver 1A, no more.
Therefore, the FET used (NDS355AN) should be more than capable, it can deal with 1.7A continuous current according to its datasheet.
My guess is that the regulator can’t provide the necessary current and/or voltage required for the “larger solenoids”. Can you provide specs for those solenoids, i.e. required voltage and current?