600-800mA seemed too low to me, assuming that the mA's are per-motor, plus some overhead for the PMC8 itself.

So... I decided to perform a test of incrementally adding and removing load.  The only convenient tool I have to measure with is the amps reported by my Pocket Powerbox's control applet.  So yes, this is a system measuring itself, and probably in 0.1A increments.  So no great precision, but still, I think, good enough to reflect incremental changes.

I did two iterations and got the same results from each.  I did not try a slew, just tracking.

With only the Powerbox and Anker USB hub (powered) connected, 0.1A reported
Connect PMC8 and its motors, 0.9A to 1.4A lo/hi reported, rapidly changing, with most values between 1.1 and 1.3A
Disconnect the DEC motor only: 0.6-0.9A lo/hi, less rapidly changing, with most values 0.7 to 0.8A
Disconnect the RA motor as well (ie: just PMC8 + USB hub overhead):  0.2A steady
Connect the DEC motor: 0.6-0.7A lo/hi
Connect the RA motor: 0.9-1.4A lo/hi, and again most values are in the range of 1.1-1.3A

Again, no great expectation of laboratory precision here, but it looks to me like (2x600)+100 = 1300mA (fluctuating) would be closer.

What do you think?

- Bob

On Sun, Aug 23, 2020, at 22:53, Jerry Hubbell - Explore Scientific VP Engineering wrote:
On Sun, Aug 23, 2020 at 05:02 PM, Robert Hoskin wrote:

Out of curiosity, though... did the amperage range I found look reasonable to you, considering the power consumption of the PMC8 itself, PLUS the steppers?
Hi Bob,

Actually the amperage should be around the 600 to 800 mA range when tracking I believe. Nowhere near 1000 mA for sure.
Jerry Hubbell
Vice President of Engineering
Explore Scientific, LLC.
jrh at
1010 S. 48th Street
Springdale, AR 72762

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home

Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras:  QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating

Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!

Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2 290M
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

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