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HEQ5 Pro Voltage drops and how to fix it.


TerryMcK
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The following may apply to any mount not just Skywatchers.

 

I have just been load testing my dual scope rig on the HEQ5Pro and noticed the red power light blinking which is normally a sign of low voltage to the mount.

The rig comprises two ZWO ASI183MM/MC cameras, 3 dew straps, the mount itself and some ancillary items like focusers and a powered USB3 hub. These are all powered via a Lynx Astro power box. When I had everything running at 100% the red power light on the HEQ5Pro started to blink.

It could be stabilized by turning down the dew straps but this is not an option in the field. The rig is powered by a 30 Amp 13.8v ham radio regulated power supply but there is probably a slight voltage drop due to length of cables which are thick. The total current draw is only a rather modest 5.7 amps at full tilt when slewing with the cameras and dewstraps at 100%.

 

I have built in a break out point on the rig to measure the voltage and found it had dropped to 10.6 volts when tracking and when slewing it dropped to 10.5v.  The mount works best at 12 volts or higher, the blinking is a normal warning to the user and shouldn't affect guiding/tracking.

To mitigate this I have bought a 12v to 12v step up/step down voltage regulator that are normally used in caravans, narrowboats etc to regulate the voltage to 12v right where it is needed - portable TVs for instance. https://www.amazon.co.uk/gp/product/B08FC4DWBC

I will install it on the rig where the outlet power to the mount comes out of the Lynx Astro box. The other power outlet feeds the camera coolers so is independent.  The dew straps are powered by their own power outlets on the Lynx box.

 

So even if the voltage drops to 10 volts the mount will still be fed with 12volts - Result.

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The output to be augmented by the voltage regulator is the orange cable in this picture 

58DE0772-DCF5-4B05-BC41-234B95952A30.jpeg

 

It is the jack under G and has the Lynx Astro label around it. There is plenty of room on the mounting plate to secure the regulator. The orange cable feeds the power solely to the mount. The other cable under F feeds the camera coolers and some ancillary components.

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One of the comments on Amazon mentions: In my testing, the voltage drops off a cliff at about 4-5A, doesn't come close to handling the rated 6A load

I would give it a full test before making it permanent. Shoot it back if in doubt.

 

Unfortunately a good number of these sort of devices fail to deliver their rated specifications.

 

Len

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5 hours ago, len2376 said:

One of the comments on Amazon mentions: In my testing, the voltage drops off a cliff at about 4-5A, doesn't come close to handling the rated 6A load

I would give it a full test before making it permanent. Shoot it back if in doubt.

 

Unfortunately a good number of these sort of devices fail to deliver their rated specifications.

 

Len

 

All ready tried it out Len. It works fine. The mount only takes just over an amp when slewing at 12v. I fed the voltage regulator with 8.1 volts and it maintained 12.17 volts at full slew. The power supply compensated by feeding more current at 8.1 volts. The measured input current was 1.4 amps. So not an issue at all for the mount.

 

Note the voltage regulator only feeds power to the mount. I have a split feed where the other cable feeds the coolers on the cameras which are not as voltage sensitive.

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On 8/8/2021 at 4:57 PM, TerryMcK said:

The total current draw is only a rather modest 5.7 amps at full tilt when slewing with the cameras and dewstraps at 100%.

In no way can I be called any type of expert when it comes to electricity, but I was interested in seeing what my rig was drawing while slewing etc. I have an Pegasus PBB, and I rarely open it, as once you have set it on auto, it remembers the settings and works without opening the software.

 

I was surprised to see it was drawing 2 amps when the camera was cooling and 2 dew heaters were operating on auto, it was only drawing 3 amps while slewing. The PPBB powers my mount, camera, dew heaters and focuser. With the EQ6 being a touch heavier than the HEQ5 and carrying a load of 15kg, I expected to be drawing something similar to your 5 amps. The voltage also never drops below 12.6v even when slewing.

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This dual rig has 2 cooled cameras and double the amount of dew straps though Brian. So everything electrically is doubled up. With a single cooled camera and dew straps the current draw is slightly more than 3 amps even when slewing.

On the dual rig the issue is not so much the current draw which is fine at 5.7 amps but the voltage drop from the power supply, which is always 13.8v, along the admittedly thick but longish cables to the mount. The resistance of the cables produce the voltage drop. Always a problem with low DC voltages. The extra power draw from the cameras cause more voltage drop, heat etc with the end result that the voltage drops even more.

 

The Pegasus PB is intelligent and probably has a voltage regulator on board close to where it is most needed and works fine. If it had been around when I bought the Lynx unit I would have spent the extra money on the Pegasus. The joys of hindsight I suppose 😀

 

However as I already have a dumb power distribution unit from Lynx it just needs a bit of extra help in the form of a local external voltage regulator, it was just under 30 quid, to keep the voltage at 12v that the mount likes. Actually, through reading the specs, the Skywatcher mounts work from 11v to 14v and start flashing when just below 11v

 

I have just wired the regulator in and pleased to say it works perfectly when at full tilt.

 

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11 minutes ago, TerryMcK said:

The Pegasus PB is intelligent and probably has a voltage regulator on board close to where it is most needed and works fine. If it had been around when I bought the Lynx unit I would have spent the extra money on the Pegasus. The joys of hindsight I suppose

Hindsight is wonderful Terry. If I had known how good they are, I would have bought the Ultimate version and done away with the powered usb hub.

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