Are you sure your supply has enough current drive? Verify your 5v stays 5v.
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- Use PIC16f877A to turn on relay and magnetic valve.Why MCu hot?
Are you sure your supply has enough current drive? Verify your 5v stays 5v.
It would be .7v at the base as oppossed to 2.5vOriginally Posted by Sceadwian
Last edited by Mikebits; 25th March 2009 at 06:49 AM.
before my 5v to MCU circuit,i got put a 10k resistor.Is that my MCU circuit must have more current?? But the way, why my relay and valve still can function,and cause the MCU very fast. If i just turn on relay,but the valve i off it,then my MCU will be fine........Please help me,3 more days i need to demonstration my project.
Are you saying you have a 10K resistor from your 5v to your MCU Vcc pin? If so remove it. Really helps to make complete drawings.
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Last edited by Mikebits; 25th March 2009 at 03:41 AM.
See why it helps to draw schematics. Can't see how you could heat up a 16F877 with a 10K on VDD though. Do you have decoupling caps? Both VDD & VSS connected? Stable regulated 5V?
Maybe it is current starved and oscillating? Who knows ???
Never used a PIC, do they go into wierd conditions with funky power?
Last CPU I designed with was the mobile pentium. Damn pain in the arse part.
Last edited by Mikebits; 25th March 2009 at 04:23 AM.
You have not shown how the PIC is connected to the supply, an EXACT schematic is essential if you want to solve the problem.
thanks
a
why must put a decoupling caps at both VDD & VSS
You did not answer my previous question about the 10k resistor. You do not need decouple caps on your ground pins, You only need decouple caps on your power pins ie. +5v
I think Blu meant caps connected from power to ground.
Last edited by Mikebits; 25th March 2009 at 05:33 AM.
now i remove the 10k resistor at the Vin place.Initially i do this is to protect my MCU burned.
So have you tested it yet? What happens now?
You need decoupling caps with any digital logic IC. 0.1uF is common. We can't help you until you provide a complete schematic of your design. Photos may help.
i try it whole day,i figure out somethings.That is,my MCU circuit and relay all no probelm,works well.Even i use relay to turn on 240V without load(mean valve),its still work.But if i connrct the 240 to my valve,problems happen.MCU hot and MCU stop function.i am using 220v ac 50hz solenoid valve.is than my valve problems???
I'll type slowly.
You need to draw a COMPLETE schematic of your project. Our crystal balls are on the fritz.
but i dono how to draw it........
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