I was just using a 18 v cordless drill battery with an ammeter connected between the motor. I was checking for binding and mechanical smoothness.....and was curious about how the amp draw would compare after I got everything connected with my PS.

I have a wall wart PS that puts out 2a @5v, and 2a @12v with a molex connector, but I have the option of having a 5v and a 12v tap on the 80v antek PS that I intend to buy as my main supply for the SnapAmp. Is there a preference over the best way to go?

The low voltage taps add money to the unit, so if there isn't a good reason to go that way I'm happy to hear it.

I assumed that I would connect the grounds together on the wall wart and the main supply if I decided not to get the PS with the extra taps.

The 80v Antek with the 5v, and 12v taps only have a 1a output for the lower voltages.....but I believe that will be enough for my setup after doing a little math.

Mike

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Michael,
>
> You should always keep the supply at 80V or below.  All SnapAmp components are rated for 100V or higher.
> Where are you measuring the current?  Is that plotted motor current?  Or are you measuring the 18V supply current somehow?
>
> Your calculation assumes that it is the supply current.  But if it is motor current then the (average) supply current should always be less than the motor current so the power consumed would be even less.  The way it works with a switching amplifier is that if the motor current is 2.25A then at times we are pulling 2.25A from the supply but at other times we are pushing 2.25A back into the supply so the average current is something less (SnapAmp PWMs at 30KHz).  If a power supply is only rated for 0.5A it may not like this.  Capacitors in the supply and in SnapAmp help smooth the currents that the supply sees.  But since they are so inexpensive in this current range I would select a couple Amp supply.
>
> HTH
> TK 
>
>
>
> ________________________________
> From: michaelthomasn <michaelniksch@...>
> To: DynoMotion@yahoogroups.com
> Sent: Thursday, May 10, 2012 2:53 PM
> Subject: [DynoMotion] SnapAmp Max Voltage
>
>
>  
> I see that the SnapAmp is rated for a max supply voltage of 80V. Can I safely use a 80V supply, since there is the max voltage clamp......or do I still need some headroom?
>
> Right now, I am simply powering my DC brushed servos with a 18v battery pack to verify mechanical operation.
>
> My Z axis is drawing 2 to 2.25 amps on the way up at 18V. If I computed wattage.....would this allow me to figure the amperage at 80V if I expected the same ipm?
>
> 18V x 2.25 = 40.5 watts
>
> 40.5 watts / 80V = .51 Amps ?????
>