Hi benemorius and indeed all others who have contributed to the thread
thanks for all the info and your valuable comments.
I am using the motor to control the speed of rotation of an equatorial platform, which is indeed a type of telescope mount, carrying a large load.
I have used these Celestron motors before, always got the speed needed at about 10% of minimum on the pot. I agree the top 25% or more of the pot does not seem affect speed at all, ie max speed plateau at at about 75% of adjustment .

Tried to view your schematic, to follow your ideas to slow the motor down but every time I click for a larger image the system just says I am not logged in ( even tho I am) and asks for me to log in again.
frustrating !
To follow Dick's advice, am I right that R5 is resistor no 5 in the block of five next to the 8 pin IC, counting away from the IC ?
Best for 2012 to all who provide free advice to confused amateurs like me ! ! !

DavidB

 

Here, I'm going to post the image of the schematic I made from benemorius' schematic.
It has a bit less white space than his, so it will be easier to work from:

Note: R9 is not in the original circuit.

If you still can't see it, then your web browser may not be accepting cookies.

Try changing your browser's settings to allow cookies.

 

Hi all,
and all the best for 2012.
I just can't believe how generous you guys are with your time !!!
To answer Benemorius , yes I am using the motor to control rotation of an equatorial platform, which is a type of large telescope mount.
And the suggestion of Dick is spot on !!
I tried a 100K resistor in parallel with R5, the one next to the 8 pin IC ( I can't open the schemetic for some reason, it just keeps asking me to log in again and again ??)
and this indeed slows down the motor at it's slowest setting by about 20 %... BINGO.
Oddly this slowing effect is highest at very low speeds and seems to taper off and is almost totally absent at the highest speed setting of the pot.
Whatever, it solves my problem nicely, THANKS DICK.
Thank you all SO much for your help and advice.
I hope Benemorius can get his motor to run faster for his application to work OK
Once again thanks to everyone who contributed ideas to this problem
Best Regards
DavidB_54

 

Hi Sgt Wookie,
your post of the diagram overlapped my reply above.
Thanks for thsi, I have the schematic now, and also a solution to my problem.
Once again a BIG thank you to all of you.
If you even need astronomy advice, don't hesitate to ask !!!

DavidB_54

 

Remember, if you run it in the summertime, the speed may get out of whack again.

I'd also suggest using a "Lithium 9V" battery. Standard 9V batteries have very little capacity for $5, and a Lithium 9V has around 8x more capacity (advertised as "up to 10x" or similar) for $15, so it's a good deal if you are stuck with the 9V battery, especially in the cold.