[Open_electroporator] pyflex_f401 v0.6 prototype #2 turn on -- USB mass storage problems
john at cibolo.com
Wed Aug 8 15:47:26 UTC 2018
Yesterday I turned on the prototype for a while, did unrelated work, looked back and the ammeter says 500mA.
It's supposed to be 20 mA when everything is set up right and between pulses. It can go to 200 mA while the
ONBOARD_18V power supply is charging up. 500 mA meant something was broken.
I found the problem is right in the ONBOARD_18V power supply, not with what is loading it. There is an external transistor used
to get the volts all the way to off when in shutdown mode that is rated at 100mA, so the normal use was baking it and it got
cooked finally. A 500mA PNP transistor, BC807-40, is in stock now, so I will substitute that one and the problem should be gone.
So that setback was just a little detail and most of those are handled now, and documented for production.
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