Gina

Great! I have an electroluminescent panel for flats. Works well.

No, the 0v of each ammeter is connected to the current shunt individually. So the 0v is effectively connected to the 13.8v supply and battery +ve.

I can't be sure of the ones I've ordered but the one I've got has an internal connection between the -ve end of the shunt and the -ve supply connection. This means that to have the shunt in the +ve side of the main circuit means the ammeter supply has to be above the shunt voltage by at least 4v.

Yes, I disable my SSID broadcast as well as using WPA encryption. I thought it was the standard recommended practice.

Haymaking round here.

For me this is mainly a "shake-down" of all the gear and if I manage to capture decent data, that is a bonus. I don't expect much clarity tonight - it's too warm.

Yes, I've used similar ones. Thought I had one but seems not. I used one to power my little digital oscilloscope from Lithium Ion batteries.

Very hazy too.

CO is showing plenty of clear sky for tonight. Or rather, it is ATM!

Ah yes, that's true. I'm considering planetary in the future. That's where I'm hoping the RPi 4 might help.

Here's a new diagram. The 24v (anything above 19v) supply could come from a buck converter or maybe a separate mains PSU. The ROR Control has to run off the backup battery so that the roof can be closed during a power cut but no imaging will occur during opening or closing the roof so interference shouldn't be a problem.

I think I would prefer to have an extra supply than to have what amounts to separate 0v and Gnd lines. It may not be necessary to have all these ammeters but it is reassuring to be able to see what each load is taking and confirm that things are working right.

That connection system was needed because the negative current connection and negative power connection on the digital ammeter are common. Of course, if I use an additional supply for the electronics of the ammeters the Gnd can be common with the negative terminal of the battery. TBH I would prefer the battery and 13.8v PSU negative terminals to be at Gnd.

Here's the amended diagram.

Oops - a mistake in the diagrams - there is no connection from the voltage negative terminal to Gnd in the total current ammeter. Anyone spot that the shunt resistor would be shorted out? 😄

You can use USB3 devices on USB2 - just that download times are greater. I'm using the USB3 ASI1600MM-Cool camera with RPi 3 in my main imaging rigs and ASI178MC (also USB3) in my all sky camera. Download time for ASI1600MM is under 10s for the full frame, even over WiFi.

Time to pack up I think. Visibility has closed in - can hardly see any lights let alone stars. Oh well, not a wasted session.

That's another bit sorted out 😀 I haven't yet got live image plate solving working as yet but that needs a good image and I haven't really had any of those.

Cleared here a bit too or rather it had where the rig is pointing (Cygnus) but just looked outside and solid cloud and mist. The stars were visible enough to allow an autofocus run to work. Image noticeably sharper.

I would have thought you might have gone for Raspberry Pi SBCs for your pier computers, James.

This shows one digital ammeter expanded to show the extra supply.

This is what I would like to have. A main ammeter to show the total current and individual ones to show the current taken by mount, imaging rig, ASC and ROR control individually. The individual digital ammeters would need a supply several volts above the 13.8v main supply if the current shunts are in the +ve rails. I could use a buck converter to provide a 24v supply, I guess, but this seems ridiculous. I could put the shunt in the -ve line for the ASC and ROR Control as these are totally separate but the mount and imaging rig share a Gnd line via USB.

Still solid cloud and it's got a bit misty too. CO has changed from clear for several hours around midnight to not clear until 8am tomorrow morning. Guess I'll leave it another hour or so then close up.

All set up ready for tonight if the clouds part... Seems unlikely ATM but who knows.

I think I may have a little problem with having a separate digital ammeter for each load from the power distribution box. My observatory wiring has one common earth or Ground connection with a heavy duty cable going from a copper earth rod, to the pier head where the mount and imaging rig supplies are earthed/grounded. From there it goes through the cable duct with other cables (the supplies to the mount and imaging rig) to the warm room and the power distribution box. Separate twin cables will feed the all sky camera and ROR motor control unit. Like the mount and imaging rig, I was planning to use a common Gnd for the other loads. Now to the problem :- The digital ammeters need a voltage source as well as the series current measuring resistance (shunt). No problem you say - connect +ve to the main +ve supply and the -ve to Gnd - but no the negatives are common on the ammeter circuit board as shown below in this circuit diagram of my current power distribution box.