Dew heater supply smoothing ?

[Epicyclus Dave]

Hi there .

I'm about to make a new , larger power box for taking to remote sites around southern Scotland.

I will be powering my NEQ-6 , Laptop ( cdc & EQmod ) and dew heaters from 1 battery , 90AH 12V AGM gel .

I was wondering if it would be wise to add smoothing for the heater circuit , i will have 4 pwm circuits pulsing away in the dew hand controller.

I have found 4 - 4700uF 25V in a component box that i was thinking of soldering onto veroboard , wiring just before the dedicated heater panel socket.

Do other single battery users find they have a supply ripple from pwm circuits affecting sensitive mount pcb's or am i perhaps thinking too deep about this .

thanks for any ideas.

Dave.

[gcraib]

If it is just the heater circuit (ie a pure resistor) then a small amount of ripple wouldn't matter.

I don't think you would see that much any way (totally subjective btw) back onto the supply from the PWM.

Capacitors will help smooth the waveform but you might find they need some time to charge up before connecting to the load, otherwise you won't get much of an output.

[Fish-Man]

You shouldn't put any capacitors in the circuit, because the PWM is a variable squarewave generator, and if you put in a capacitor, the squarewaves will become a sawtooth type waveform as the capacitors try to rectify the output, and the "average voltage" coming out of the unit will rise, then, depending on the value of the capacitors in relation to the frequency of the PWM, you may end up with no control of the output, as the PWM's squarewave is rectified into a flat voltage. (what a sentance )

if that makes sense .........

Regards,

Paul

[woodbob123]

Will you be using a dc-ac inverter between battery and laptop or running direct from battery

[Auntystatic]

Put the capacitors in parallel on the supply side of the dew heaters, they will charge almost instantly and act as a buffer/reservoir and smooth the ripple somewhat, they won't affect the operation of the dew heaters in anyway whatsoever.

[Epicyclus Dave]

Hi , thanks all , ive done a wee diagram of between the battery and the cigar sockets .

My current diy box i built last year has 2 x 22AH AGM batteries , one for heaters and one for mount etc & diy battery low led indicators , im converting to a larger capacity 1 battery setup with the 90AH AGM , i'll mount a cigar socket with smoothing and label it Heaters , i've still to make a 4 channel controller as well , phew , id better get wiring , the dark nights are coming fast

Going to make a start at the weekend in the shed building an insulated carry box from plywood, also including some warm plates for the battery to fool it into thinking it's in the house when it will really be outside in winter time, heh ( i've wanted to solve my problems with battery capacity on very cold nights , hope this works , snug battery .

Dave.

[woodbob123]

Hi with a simple layout like that should be no need for the extra capacitors, battery it's self will smooth any supply flucuations . Plus in the laptop supply will be smoothed as well

Bob