Performance/startup issues with Celestron dual-axis motor drive for CG-4

[SalehRam]

Hello all,

I started to get a strange behavior since yesterday with my motor drive for my CG-4 mount.

I have been using it with the normal one time use D-cells. Yesterday I wanted to make a new battery pack to hold 5 rechargeable D-cells.

Now to give a full explanation on the whole point that I'm working on, please check the points below:

• The controller is said to need 6v power which is also printed on it as well
• After further research on the actual stepper motors in this package, I found out that they are actually not receiving their full power since they are rated at 19v, but they get only 6v from the controller
• I have been measuring the output voltage the one time use D-cells give, and it gets up to 6.6v or 6.7v. If the voltage dropped below that, the motors won't start and the light will stay red in the controller.
• 4 rechargeable D-cell will give me 5.4v at max (assuming each one is outputting 1.35v at full charge). This is no where near the required AND OBSERVED requirements... So I had to add another battery to get the voltage to 6.7v
• This is in the same volt range that I get from the one time use batteries.
• When I connected my setup to the controller at the beginning its light got to green, then after a few seconds of waiting the motors started to work.
• I checked the voltage on the batteries and I found out that it is dropping to 6.6v so by now I was getting the same voltage as I was from the one time batteries
• I stopped the tracking then started it again and things got weird a little bit, the light is on green and the RA motor does not start tracking at all. If I wait a little bit or press some buttons on the controller, the light will turn red and the RA motor will start tracking very slowly.
• I can still control the motors with the buttons and they will respond but the light will stay red even if I restart it, I'll go through the same process in the above point.
• The same behavior usually happens when the one time use batteries are dropping in voltage and are approaching their limits to power the controller and motors

My issue is, I know there is a micro-controller or some sort of a brain inside the control box, but I'm not exactly sure why it is acting like this. I am confused also about the power requirements by the controller and motors. It is rated for 6v but will never work on 6v with me, I'll always have to go up to 6.7 or if I am just putting a brand new 4 D-cell batteries (6.8v).... But even with the power I was feeding it (6.7, 6.6, and risked a bit with 6.8) I was unable to understand its behavior and what is going on...

Could be possible I actually got a defective unit? or it is just the same for everyone else with this motor drive set?

Really appreciate any input or help

Regards

[Alien 13]

I cant comment on the Celestron version but the very similar Skywatcher model is quite happy running on lower voltages, in fact I power mine from a mobile phone battery bank which outputs 5.2V at 2A with no issues.

Alan

[SalehRam]

37 minutes ago, Alien 13 said:

I cant comment on the Celestron version but the very similar Skywatcher model is quite happy running on lower voltages, in fact I power mine from a mobile phone battery bank which outputs 5.2V at 2A with no issues.

Alan

Well, I looked around and found out the SkyWatcher model to be identical to the Celestron model... I take it both are for the same mount right?

I'm might actually look into the specifics for the SkyWatcher one as I'm starting to get into the frustration area with this one..

[Alien 13]

Just now, SalehRam said:

Well, I looked around and found out the SkyWatcher model to be identical to the Celestron model... I take it both are for the same mount right?

I'm might actually look into the specifics for the SkyWatcher one as I'm starting to get into the frustration area with this one..

The only thing worth checking is to see if the Celestron version has a protection diode fitted, this would drop 0.6V or so from the input supply.

Alan

[lenscap]

One-time alkaline batteries only produce their nominal voltage when fully charged. A one-time D cell will only produce about 1.25 volts when 50% discharged.

So a system designed for 4 D cells should work happily at 5 volts or a bit less.  I suspect there is an excessive voltage drop somewhere, maybe a loose or badly soldered joint.

Rechargeable NiMH cells produce about 1.2 volts until almost empty so your system should be OK on 4 rechargeables.

[SalehRam]

1 hour ago, lenscap said:

One-time alkaline batteries only produce their nominal voltage when fully charged. A one-time D cell will only produce about 1.25 volts when 50% discharged.

So a system designed for 4 D cells should work happily at 5 volts or a bit less.  I suspect there is an excessive voltage drop somewhere, maybe a loose or badly soldered joint.

Rechargeable NiMH cells produce about 1.2 volts until almost empty so your system should be OK on 4 rechargeables.

Quote

The only thing worth checking is to see if the Celestron version has a protection diode fitted, this would drop 0.6V or so from the input supply.

Alan

I'm going to try and peek inside the control box and check for anything looks not OK in the soldering... I'm not sure what will I find but I've removed the power plug port and looked inside, I saw a lot of diodes... So maybe they are causing the differences in actual power consumption vs what I was expecting...

[Zombie74]

the same problem, I already change all the batteries, rechargeable, alkaline, regulator and nothing! it's frustrating