DC supply for controller

[chand00786]

Dear all,

I want to power up a pic micro controller from 12V Battery which is about 30 feet away from the micro controller.when I connect the battery with the controller power supply section with 30 feet long wire,micro controller does not work properly.It restarts again and again after small intervals.But when, I bring the controller circuit near the battery (about 1 feet away from battery) it works properly and controller does not restarts.What should i do to solve this problem?

 

[tpetar]

Dear all,

I want to power up a pic micro controller from 12V Battery which is about 30 feet away from the micro controller.when I connect the battery with the controller power supply section with 30 feet long wire,micro controller does not work properly.It restarts again and again after small intervals.But when, I bring the controller circuit near the battery (about 1 feet away from battery) it works properly and controller does not restarts.What should i do to solve this problem?

Hi Chand00786,

You cant power uC with direct 12V, but you can use voltage regulation to voltage needed for your uC, usually 5V or 3,3V. Voltage regulation to that lower voltage should be near uC circuit with bigger capacitors.

I suppose cable wires are ok, and there is no interruption.

Additional use 100nF near uC pins for Vdd/Vss.


Best regards,
Peter

:wink:

 

[betwixt]

If the wire length is between the battery and the power supply, add a 1,000uF capacitor AND 100nF capacitor in parallel across the input (battery) side of the power supply at the power supply end. If the wire is between the power supply and the controller circuit, add 100nF and I would suggest 10uF in parallel close to the controller.

It sounds like either you are drawing enough current to cause a voltage drop in the wires or their impedance is high enough to make the power supply unstable. The capcaitor will help to fix that.

Brian.

 

[chand00786]

If the wire length is between the battery and the power supply, add a 1,000uF capacitor AND 100nF capacitor in parallel across the input (battery) side of the power supply at the power supply end. If the wire is between the power supply and the controller circuit, add 100nF and I would suggest 10uF in parallel close to the controller.

It sounds like either you are drawing enough current to cause a voltage drop in the wires or their impedance is high enough to make the power supply unstable. The capcaitor will help to fix that.

Brian.

Dear I have put a 1000uF capacitor at power supply side but problem is still there.Even I have tried with 6800 uF capacitor but controller still restarts.Actually the battery is connected with a generator.At the time of generator start,the motor of generator may draw enough current but when generator starts,motor stops and so there is no more load on battery in this condition but controller still restars again again.
One more question can you please tell me why to put 100nF Capacitor in parallel with 1000 uF capacitor?

 

[Electro nS]

One more question can you please tell me why to put 100nF Capacitor in parallel with 1000 uF capacitor?[/QUOTE]

high value for low frequncy noise . and low capacitance value (100nF) for high frequency spikes .

i still believe that what the guys suggested is good . can you provide as with more details , are you using a regulator or 12v directly to the microcontroller

another question if you have an oscilloscope or multimeter check the voltage on the VDD pin on the microcontroller an see how stable is this voltage when the generator is charging the battery . the supply voltage unstablility is one of the main resons circuits donot work .

Also check if MCLR pin is connected to 5v . also all VDD of controller should be connected to each other , same for Vss .

in addition the 100nF capacitor is very very very impirtant to have between VDD and VSS and AS CLOSE AS POSSIBLE to the controller , if you place that near the battery it is not suffcient .

hope that helps

 

[betwixt]

Agreed - large value capacitors are almost always electrolytic and these have poor performance at high frequency. Ceramic capacitors are much better at high frequencies but canot easily be constructed to give large values. If you use a parallel combination it gives best performance at low and high frequencies.

Please show us your schematic and point out where the long wire lengths are on it.

Brian.