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Topic: How do I prevent video interference caused by electric motors (Read 6 times) previous topic - next topic

dc42

Connecting a large capacitor across the output of a power supply will cause a brownout on any power supply. Connecting a heavy resistive or resistive/inductive load will not, if the power supply is adequate.
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oric_dan

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A brown-out indicates that the power supply (and regulator, and the circuit connecting all this to the load) isn't capable of supporting the load being placed on it.

This is not necessarily so, as already indicated several times. If the power leads are long and
have too much inductance, then you get large swings in voltage - at the load - with switched
load currents. That's what the info about the "Main Capacitor" was talking about.

Many good power supplies deal with this problem by running sense wires from the P/S straight
over to the load, so they can measure the voltage fluctuations and compensate. Negative
feedback stabilization.


HazardsMind

@oric_dan(333)

Yea but that doesn't explain why the normal batteries have the same problem. I understand the use of the Main capacitor, to get rid of any voltage spikes or dips. But if the power supply doesn't have enough current to supply to everything as it is, then the capacitor won't have enough charge to do its job.

Now if he had access to an adjustable voltage supply, then he could rule out the power supply he is currently using. All he has to do is set the voltage to 12 volts and adjust the current, and keep monitoring it until he gets no brown outs or interference. Then get a proper power supply based on what he measured.
Created Libraries:
TFT_Extension, OneWireKeypad, SerialServo, (UPD)WiiClassicController, VWID

oric_dan

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Yea but that doesn't explain why the normal batteries have the same problem. I understand the use of the Main capacitor, to get rid of any voltage spikes or dips. But if the power supply doesn't have enough current to supply to everything as it is, then the capacitor won't have enough charge to do its job.

Yeah, if the power supply can't supply enough current, that's certainly needs to be fixed.
I thought OP was using a huge old PC supply.

Also, the business with the Main Capacitor is an illustrative point. It works best *IF* your
controller is competently designed, and then helps deal with the battery leads, which may
be longish for any #of reasons. OTOH, if everything in the ckt has long leads with nontrivial
inductance, then the cap probably won't do much.

Good design is a systems-level solution. Would be interesting to know how auto manufacturers
deal specifically with the brownout problem when the starter motor cranks. I imagine there's
a lot of brownout protection cktry inside the computer box.


HazardsMind

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Yeah, if the power supply can't supply enough current, that's certainly needs to be fixed.
I thought OP was using a huge old PC supply.


No its like a laptop supply

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I imagine there's a lot of brownout protection cktry inside the computer box.


Im sure, but will they share it with us, probably not.
Created Libraries:
TFT_Extension, OneWireKeypad, SerialServo, (UPD)WiiClassicController, VWID

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