NEQ6pro - operating current/ Battery life

[Merlin66]

Here's the full answer for the techies:

Quote"

That's an easy one.

Because the motors are stepper motors and are being feed from a PWM

(pulse width modulated) signal even when not tracking they are still

getting a 50% duty cycle PWM signal. This locks them in place. So

even at rest both motors still draw lets say for example 0.3A. Once

you start the RA motor tracking it's duty cycle varies and you end up

using a little more current on that one motor. So you get 0.3A + 0.3A +

0.2A (the little extra needed for tracking). So while tracking you

have one motor drawing 0.3A and one drawing 0.5A. During a slew they

both end up at 0.6A and there you have it.

In a shorter answer the motors are never really off while the mount is

initialized. The noise you hear before anything starts moving is the

25Khz PWM signal going to the motors to lock them in place. They did

us a favor by doing this as it uses about 50% less power and still locks

the motors.

" Unquote

2nd installment:

Quote"

The high speed

switching regulator and many filtering components (caps and inductors)

do a very effective job and providing a smooth source of power to the

3959 PWM controllers. Those in turn have a charge pump voltage

regulator that kicks up to around 40 volts. In the end the current

being drawn off the power supply is nice and even based on the present

load or operation.

My mount draws around 4.8 watts at power up, around 14-15 watts during

two motor slews and around 8 watts while sidereal tracking. Wattage

readings are more meaningful as current measurements are going to change

with the voltage being supplied. The regulators on the motor controller

will draw more current as the voltage decreases. They do this to

maintain the same resulting voltage internally and in turn the same

wattage.

" Unquote

Sounds easy .....Doh!

[themos]

I tried using PWM to limit the power needed to run a stepper. There's issues with the back-emf generated by coils when you turn off the current. I guess they've allowed for this.

[SteveP]

Ken

Well that explained everything clearly!

From the final paragraph of the response, it indicates a total current draw of about 6.5amps during tracking and about 1.2amps during 2 motor slewing. This therefore suggests that a 2amp PSU would be more than adequate for the EQ6. I have my doubts!

Steve

[Merlin66]

Steve,

Think you have a typo should be 0.65A not 6.5A;)

Notwithstanding all the great explanation, I'm comfortable with a 5A PSU at home and the 20Ah batteries away.

Ken

[SteveP]

Ken

You're quite correct. Sums were never my strong point!

When I get a mo sometime, I'm going to connect a 2amp psu to my EQ6 .. and feel how warm it (the psu) gets!

Steve

[Merlin66]

What we really need is a recording ammeter to double check and confirm the current draw I've been given.

[Glider]

My Rapid PS3025, 0-30Vdc 2.5A power supply copes fine, the ammeter on the front shows values that agree with Merlin66.