Splitting 2 PSU

[SimM]

I have 2 regulated PSU 6A at 12v.

 

How should I split the power:

1. Colour cooled camera 3A (typically <1 amp);
2. Dew heaters 17W + 4W + (optional second 4W);
3. Mount 4A;
4. Focuser 1-2A.

Is a dew heater “noisy”? Is 17W at 50% 2x  the same as 17W - what does PSU see/need?
 

the cooled camera - does it need to be a c”clean” PSU or is it regulated for camera and USB hub?

[teoria_del_big_bang]

Are both power supplies the same and are both a smooth 12V?

If both are the same I would make it easy and supply the mount with one supply and then use the other for everything on the mount, that way the cable runs are simple  - one to mount and one to the rig itself. Although if you add everything up on the mount it is just slightly over 6A (even with 2nd 4W dew band) this is an absolute maximum and I would be surprised if the mount takes anywhere near 4A, if its a very big mount then I guess it may do when slewing but surely not when tracking (I have no idea what mount it is so only making an assumption here) and the focuser is not going to be taking 2A when at rest and again this seems quite high for a focuser so I am thinking this is a big rig ?.

Is 17W at 50% 2x  the same as 17W - Didn't quite understand the question - are you saying you have two 17W dew bands but running with the controller set at 50% ?

I see no reason why dew band would be noisy unless there was a bad connection that was arcing or kept momentarily going open circuit. They essentially have no components in them to create any electrical noise as they are just some for of  resistance in the form of a series of resistors or some nichrome wire. But some forms of controller to regulate the temperature could cause a small amount of noise depending how they are controlling the voltage but I doubt this is anything significant to worry about. 

Not sure just what camera you have so not sure what the 12V is used for but i suspect only the cooling circuit and the camera itself will work taking power from the USB so a very clean 12v supply not strictly necessary, I just like to not run the USB back via a hub is at all possible and have a dedicated good quality USB lead directly back to the computer.

Is the US hub powered ? 

Steve

Edited November 29, 2020 by teoria_del_big_bang

[SimM]

On 29/11/2020 at 21:03, teoria_del_big_bang said:

Are both power supplies the same and are both a smooth 12V?

If both are the same I would make it easy and supply the mount with one supply and then use the other for everything on the mount, that way the cable runs are simple  - one to mount and one to the rig itself. Although if you add everything up on the mount it is just slightly over 6A (even with 2nd 4W dew band) this is an absolute maximum and I would be surprised if the mount takes anywhere near 4A, if its a very big mount then I guess it may do when slewing but surely not when tracking (I have no idea what mount it is so only making an assumption here) and the focuser is not going to be taking 2A when at rest and again this seems quite high for a focuser so I am thinking this is a big rig ?.

Is 17W at 50% 2x  the same as 17W - Didn't quite understand the question - are you saying you have two 17W dew bands but running with the controller set at 50% ?

I see no reason why dew band would be noisy unless there was a bad connection that was arcing or kept momentarily going open circuit. They essentially have no components in them to create any electrical noise as they are just some for of  resistance in the form of a series of resistors or some nichrome wire. But some forms of controller to regulate the temperature could cause a small amount of noise depending how they are controlling the voltage but I doubt this is anything significant to worry about. 

Not sure just what camera you have so not sure what the 12V is used for but i suspect only the cooling circuit and the camera itself will work taking power from the USB so a very clean 12v supply not strictly necessary, I just like to not run the USB back via a hub is at all possible and have a dedicated good quality USB lead directly back to the computer.

Is the US hub powered ? 

Steve

Thanks for the reply Steve. They are both Modern Astronomy 12V 6A regulated PSU. They are supplied with QHY cameras. My cameras are main ZWO ASI294MC and QHY5III178M for guiding.

I read that you cannot put two PSU in parallel to get 12V 12A (but you can stack them for 24V and 6A). That's because the output varies slightly. Mine deliver 12.05V and 12.15V and unless they are designed for it, one will suppply the current and one will kill the other (apparently).

I think the mount is the critical one. I have a SkyWatcher EQ6-R PRO and the mount requires a good PSU. My understanding is that the motor circuitry is not that clean. The spec is a bit vague but the mount needs 2.5A at 15V and 4.5A at 11V. So I figured about 4A at 12V.

This is maximum, so the mount takes much less when not slewing. Sharing the PSU with an electric focuser makes sense because you don’t slew and focus at the same time!

The other PSU can power the camera cooling and dew heaters. 17W and two 4W heaters is a maximum of 2.5A and the camera cooling is typically ably 1A and not the maximum of 3.5A from the spec. I’m not sure how well a PSU can cope with PWM (on/off) varying loads?

Edited December 14, 2020 by SimM

[SimM]

On 29/11/2020 at 21:03, teoria_del_big_bang said:

Are both power supplies the same and are both a smooth 12V?

If both are the same I would make it easy and supply the mount with one supply and then use the other for everything on the mount, that way the cable runs are simple  - one to mount and one to the rig itself.

I did split it like this. A waterproof mains PSU box on the ground with an internal 3-pin socket for a WiFi extender.

One PSU for a Dew Controller on the Mount Spreader Table - with 12V outlet for the Mount.

Second PSU runs up to the rig where it splits/powers "everything". This is a 12V Mini PC, Focuser, EFW and main Camera Cooling.

One "up" heater cable to the OTA Dew Heater and one "down" USB cable to the Mount.

Both PSU run cool because the running power is far less than the often quoted maximum power ratings.

The "secret" for cable management is to combine/distribute 12V Power and USB to the two "zones" with cables that are long enough, but not too long to get tangled.

Simon