Odd ball BS2 voltage regulator question.
Martin_H
Posts: 4,051
What would happen if you connected the BS2's Vin pin to 7.2 volts and the Vdd pin to 5 volts regulated power? Would it work normally or would current be drawn from the BS2 by the rest of the circuit instead of the other 5 volt source?
The reason I ask is that I have an old Board of Education rev A. Unlike rev C the Vin pin is unconnected, while Vdd is connected to the BOE's 5 volt regulator. I've considered modifying this board so Vin is connected like rev C, but will I need to cut the trace from the BOE's regulator to Vdd? Would I also need to add a 1000 uf cap like rev C?
At this point I imagine the astute reader is asking themselves "why fiddle with the BOE's power connections the stamp won't care?!" The answer lies in my desire to conduct an experiment with another 24 pin microcontroller (not from Parallax) which was designed with the rev C in mind and only accept power from Vin and not Vdd.
Obviously I could try this with my rev C board, but that board is being used and my rev A is idle. So you conduct an experiment with the BOE you have, not the BOE you want or need.
The reason I ask is that I have an old Board of Education rev A. Unlike rev C the Vin pin is unconnected, while Vdd is connected to the BOE's 5 volt regulator. I've considered modifying this board so Vin is connected like rev C, but will I need to cut the trace from the BOE's regulator to Vdd? Would I also need to add a 1000 uf cap like rev C?
At this point I imagine the astute reader is asking themselves "why fiddle with the BOE's power connections the stamp won't care?!" The answer lies in my desire to conduct an experiment with another 24 pin microcontroller (not from Parallax) which was designed with the rev C in mind and only accept power from Vin and not Vdd.
Obviously I could try this with my rev C board, but that board is being used and my rev A is idle. So you conduct an experiment with the BOE you have, not the BOE you want or need.
Comments
I would modify the rev A board to work like rev C. The 1000uF capacitor is there mostly to help stabilize the BS2's 5V supply if there's a brief interruption in the Vin supply. You could mostly manage without it. You'd have to connect Vin to the BS2's Vin pin and cut the trace between the BS2's Vdd pin and Vdd.