looking for a schematic

[artur_p]

Hi guys, I'm looking for a schematic of a voltage damper circuit.
I have a 10VDC signal that is fluctuating every few seconds and i'm looking for a circuit that would eliminate that fluctuation.
thanks for your help.

 

[Nigel Goodwin]

Hi guys, I'm looking for a schematic of a voltage damper circuit.
I have a 10VDC signal that is fluctuating every few seconds and i'm looking for a circuit that would eliminate that fluctuation.
thanks for your help.

You need to provide a lot more information, like:

What is the source of the 10V DC?.

What is it feeding?.

What current is been taken?.

Why is it fluctuating?.

 

[grrr_arrghh]

I've seen this type of problem solved by getting some batteries, and using the supply to charge the batteries, while using the batteries to run whatever it is (as a sort of regulator) - it was something along those lines anyway

 

[Styx]

err arnt you just using the batteries as caps in such an arrangement?

cant you just use soemnice electrolytics to smooth out any ripple and also as local tank capacitance

 

[Nigel Goodwin]

err arnt you just using the batteries as caps in such an arrangement?

cant you just use soemnice electrolytics to smooth out any ripple and also as local tank capacitance

Yes, but we don't know anything about the requirements!.

 

[artur_p]

the source of the 10V signal is from a air flow station which varies depending on the speed of the fan 30% speed = 3V, 60% speed = 6V, 100% speed = 10V. this signal is sent to a variable frequency drive that runs the fan and it needs to be stable, but what happens is that the voltage drops down to 0 for a split second, this happens unpredictably and frequently. i need a very simple circuit that would get rid of this voltage drop. something like the circuit for the fuel gauge in the car, all the fuel splashing around in the tank but the needle doesn't fluctuate.
thanks.

 

[Nigel Goodwin]

There's still not a great deal of information, but at least we now know it's not a 10V supply, it's actually a varying signal from a transducer - which rather kills the battery idea :lol:

The obviously solution is to add capacitance, the value depends on many factors (none of which we know) so you will have to determine the value experimentally. You may also need to feed it through a diode, so it doesn't discharge back through the source.

I should try a 100uF for a start, and see what difference that makes.

 

[ante]

Hi

To add capacitance is the way to go but the diode will drop .6 Volts and this must be compensated for.

Ante :roll:

 

[Styx]

diode drops are something we have to live with.

A diode is needed since the Cap with be charged to somewhere round 10V - Actual level based on load, input ripple and what diode used.

The input voltage will be changing, thus when its level drops below the level of the cap it will start to discharge into the source. Depending on the imedance of the source would determine how far the cap would discharge with no diode. A diode is needed!!

You could get away with using Schottky diode but they come at a price (reverse recovery is a serious one) but as already stated we have no real info on the cct operation ie how much power are you expecting to draw from this derived voltage rail. It might turn out that a Schottky is perfect for you.

More info please.

 

[jem]

You would still need some kind of bleeder resistor across the capacitor. Otherwise, the circuit will tend to act more like a peak detector is the capacitor has no way (through the source or the load side) to discharge.

Maybe you should consider an integrator, or low pass filter. The corner frequency is set to follow the changes in the input while ignoring sudden changes.

 

[ante]

An OP as integrator can fix the problem, and no voltagedrop will occur.
Then a very low value cap will do fine as buffer.

Ante :roll:

 

[Styx]

Er no because when the voltage is stable the integrator will integrate off thus not show the "filtered" component - remember the integral of a constant is a ramp.

just use an OPAMP set up as a buffer then use an RC filter.

I was under the impression that the 10V was used as a source of power and NOT a reference/control feedback kind of signal.

If it is a control like signal that depending on the level something must happen - use the OPAMP buffer -> RC filter

If it is something that generate a power rail but fluctuates - diode block and tank capacitor it.

 

[artur_p]

thanks for all your ideas and replyes.

 

[artur_p]

I tried the RC filter and it works really good, the only thing is it drops the voltage by a couple of volts but thats ok because i can boost the output signal.
thanks for your help.