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Need help understanding how to power my board

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robismyname

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lm2941

I have a board that I need to power up with DC voltage. Not sure what pin or pins I need to connect to. Can someone help me? I provided the schematic.
 

It needs 10V or above at J2, Pin 2 is positive, pin 1 negative.
 
FvM,

What is P1 pin 16 listed as 7.7 Volts telling me?

And why is C3 (22 micro Farad) in series with pin 2 of J2?

Robismyname
 

Hello,

don't know what's the overall function, but VR1 is a voltage regulator programmed to a 7.7V output voltage by R6/R7. To achieve this output voltage, the device needs a somewhat higher input voltage, maybe 10 V. Cause the input is also connected to J1 and P1, there may be additional max. and min. requirements from external connected devices, that can't be seen from this schematic. An input bypass cap as C3 is generally necessary with voltage regulators.

Regards,
Frank
 
J2 is the input to the Voltage regulator (VR) LM2941:
https://www.selectronic.fr/includes_selectronic/pdf/NS/LM2941.PDF

The LM2941 is a voltage regulator that its output is sense by
U1(MC34164) and this put a reset signal out on pin10 of P1.
**broken link removed**
The MC34164 is an undervoltage sensor.

7.7 V is the minimum voltage that the sensor will send an
reset signal out.
 
i need to know what funtion is c3 performing. U explained why we need it but i need to know what it is physically doing to the voltage or current?
 

C3 is not in series, it is in parallel. Maybe is just
for filtering glitches or transients....
 

J2 pins are not labeled on the board so I didn't know what is pin 1 and what is pin 2. What would happen if Pin2 was negative on Pin1 was? Will anything blow up or catch fire?
 

Most likely something get damaged with wrong polarity. Normally J2 Pin 1 should have a marking, e. g. a rectangular PCB pad. But to be sure, you can test with an ohmmeter, the said C3 has a polarity mark. Juyt trace the connection.
 

Hate to keep beating a dead horse but why is C3 22micrfarad? What was the rationale used to determine the value of the capacitor?
 

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