Hello everyone,
I have taken a circuit from breadboard to PCB and I am having some issues with a few components. The device is a power controller designed to monitor 2 batteries. 1 battery is a backup battery and the other is the main battery. The main battery is also a starting battery for an engine. The power controllers job is to make sure that the main battery never drains past the point where it would no longer have the ability to start the engine. At the threshold where the main battery get's cutoff, say 12v, the backup battery is now the source of power down to it's own cutoff threshold, also 12v, at which point the power controller will shutdown the PC that is being used to log data. Hopefully that in a nutshell provides enough information to help me with an issue I am encountering.
I had 4 of these PCB's created with the limited knowledge I have in this area as well as leaning on various information available online. 1 of the completed PCB's does exactly as it is supposed to do and the other 3 do not. To make matters worse or maybe better in terms of problem solving, the other 3 exhibit the same exact behavior. I have 2 p-channel mosfets (FQP27P06) and 2 darlington transistors (BC517) used to turn on/off the mosfets.
On the working unit I am observing the following voltages:
Mosfet 1:
G: 0.658v
D: 14.65v
S: 14.65v
Transistor controlling Mosfet 1:
Collector: 0v
Base: 1.407v
Emitter: 0.656v
Mosfet 2:
G: 0.657v
D: 14.65v
S: 14.65v
Transistor controlling Mosfet 2:
Collector: 0v
Base: 1.405v
Emitter: 0.655v
On the other 3 units I have a variation of the following with the exact same behavior:
Mosfet 1:
G: 8.1v
D: 13.82v
S: 13.82v
Transistor controlling Mosfet 1:
Collector: 0v
Base: 0.77v
Emitter: 8.09v
Mosfet 2:
G: 8.11v
D: 0.001v
S: 13.82v
Transistor controlling Mosfet 2:
Collector: 0v
Base: 0.77v
Emitter: 8.11v
What I am hoping is that someone could look at my novice built PCB's and tell me what may be causing this from a layout or component choice perspective as well as if I am breaking any major dos or don'ts for PCB design. I hope I have provided enough info to do this but if not, please feel free to let me know what other info would be helpful, and lastly, please feel free to tear this apart, so I can get better at this stuff.
Thanks!
I have taken a circuit from breadboard to PCB and I am having some issues with a few components. The device is a power controller designed to monitor 2 batteries. 1 battery is a backup battery and the other is the main battery. The main battery is also a starting battery for an engine. The power controllers job is to make sure that the main battery never drains past the point where it would no longer have the ability to start the engine. At the threshold where the main battery get's cutoff, say 12v, the backup battery is now the source of power down to it's own cutoff threshold, also 12v, at which point the power controller will shutdown the PC that is being used to log data. Hopefully that in a nutshell provides enough information to help me with an issue I am encountering.
I had 4 of these PCB's created with the limited knowledge I have in this area as well as leaning on various information available online. 1 of the completed PCB's does exactly as it is supposed to do and the other 3 do not. To make matters worse or maybe better in terms of problem solving, the other 3 exhibit the same exact behavior. I have 2 p-channel mosfets (FQP27P06) and 2 darlington transistors (BC517) used to turn on/off the mosfets.
On the working unit I am observing the following voltages:
Mosfet 1:
G: 0.658v
D: 14.65v
S: 14.65v
Transistor controlling Mosfet 1:
Collector: 0v
Base: 1.407v
Emitter: 0.656v
Mosfet 2:
G: 0.657v
D: 14.65v
S: 14.65v
Transistor controlling Mosfet 2:
Collector: 0v
Base: 1.405v
Emitter: 0.655v
On the other 3 units I have a variation of the following with the exact same behavior:
Mosfet 1:
G: 8.1v
D: 13.82v
S: 13.82v
Transistor controlling Mosfet 1:
Collector: 0v
Base: 0.77v
Emitter: 8.09v
Mosfet 2:
G: 8.11v
D: 0.001v
S: 13.82v
Transistor controlling Mosfet 2:
Collector: 0v
Base: 0.77v
Emitter: 8.11v
What I am hoping is that someone could look at my novice built PCB's and tell me what may be causing this from a layout or component choice perspective as well as if I am breaking any major dos or don'ts for PCB design. I hope I have provided enough info to do this but if not, please feel free to let me know what other info would be helpful, and lastly, please feel free to tear this apart, so I can get better at this stuff.
Thanks!
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