Gina

Do you mean stepper motors?

Checked source code and it looks alright. I'll shut down and unplug the HAT and check the GPIO pin with nothing connected. A fault on the power side of the opto-coupler cannot affect the data side (RPi) so I can't have blown the GPIO - that's the whole point of using the opto-couplers.

Found a dry joint which I've fixed. Dew heater now working and so is the control. One problem fixed. Cooling control still not working and found reason is that GPIO12 which now controls the cooling is not going high. Reading 0.15v so not shorted to Gnd. Going to check the code...

Testing... Imaging at 32µs with gain at 0 as usual for daytime. Camera is reporting 12.3°C. Lower level cooling satisfactory. Switching to full cooling - nothing happening so I have something wrong. Checking dew heater - not working - off to investigate - back shortly...

Circuitry completed and now testing. A couple of photos.

Ooh! A quieter chainsaw - I love it ?

Yes indeed. I have made several remote controlled focusers with both Arduino Nano and Raspberry Pi and stepper motors. I use 3D printed brackets designed to suit.

Found and corrected the fault on the ASC but there are also modifications which I've been working on. Still more to do so won't be working on the weather station for a day or two.

Been working on the control circuits on the RPi HAT. Started by removing redundant components - mostly unused connectors, leaving a nice lot of space for the cooler control circuit. Nearly finished but stopped for the night. I'll take and post a photo tomorrow plus a layout diagram probably.

A great day's work James - well done ??

Chassis mounting connector (previously called socket) now mounted in side of box, +13.8v and power ground connected. Next is to change the control circuitry for the cooler. It looks like the dew heater circuit is easier to change so I might swap the controls over. I already need to change the driver code for the reversed logic so I can change the controls over at the same time.

Socket connections (actually the socket has pins so maybe it's a plug ) :- Power Gnd - Green +13.8v - Yellow Heater - Orange Cooler - Blue

Plug connections :- Gnd - Green (Cooler -ve) +13.8v - Yellow Heater - Orange Cooler - Purple

If I were to use an ordinary rectifier diode it would drop around 0.9v so I've set the volts to 4.1 and the camera temperature has settled down the about 13°C. Still satisfactory. Found a couple of 1N4005s - 600v 1A. Put one in series with the bench PSU and set it to 5v. Camera still reporting 13°C. Satisfactory. Searched high and low for the 4 pin sockets without success then I thought of looking in my astro box and found one on a box I had originally set up as a dew heater distribution box which I no longer want.

Test begun. Starting temperature 23°C. Peltier TEC connected to 5v. Camera temperature coming down... 16°C... 12°C... Dropped voltage to 4.6v to represent the +5v rail with a Schottky barrier diode in series with the Peltier TEC. Temperature has crept up to 12.3°C but I doubt it will go up more than a few tenths more. Imaging at 32µs with gain at 0 as usual for daytime. Cooler is in still air at around 23°C. Camera is now reporting 12.5°C. Camera temperature going down again - still imaging - maybe the ambient has dropped a bit - cloud has arrived. Camera is now reporting 12.1°C. No hot pixels or noise to be seen so this will do nicely. EDIT - Camera is now reporting 11°C. Peltier TEC current is just under half an amp. Cooler feels barely tepid. Test Successful.

Found the reason the dew heater wasn't working - broken connection. Now to check how much cooling is required for daytime to keep the camera at a reasonable temperature.

With the Peltier TEC now being connected to power Gnd instead of the +13.8v rail and the dew heater to the +13.8v rail, I shall need 4 wires from the control box to the ASC unit instead of 3. I have 4 pin connectors same as I use for the power on my astro imaging control boxes (originally bought for a project I didn't pursue). These are screw on types like the power connector on the EQ8 mount (except that has 2 pins). So that's the connectors decided.

Here's a circuit diagram for the camera cooler control. With GPIO13 at logic 0 (0v) the opto-coupler is off and the P channel MOSFET J438 gate is at 0v with respect to the source and no current is supplied to the TEC from the 13.8v supply but current is supplied through a diode from the +5v line producing a small amount of cooling. When GPIO13 goes high, current flows through the LED in the opto-coupler, turning the photo-transistor on and taking the MOSFET gate to -13.5v w.r.t. the source turning it on. The TEC is now supplied from 13.8v and on full. The diode to the +5v line is reverse biased. With this circuit the control logic is inverted compared with before and the driver code will need altering to suit.

Been checking the dew heater control circuit and the fault is between the opto-coupler and the MOSFET so I'll shut down and examine it close up. I want to change the cooling control circuit so I think I shall re-work that area of the RPi HAT - it's very crowded.

Added the Astroberry Board driver to the startup command and it's working. I altered the code to suit my controls for camera cooling and dew heater (the advantage of open source).

Set up indoors on table and it's all working except for the dew heater. The cooling is constantly on because the Astroberry driver is not selected ATM. I'll fault-find the dew heater with my DMM. I want a lower amount of cooling for daytime and will work on the circuit design. I'm not happy with the in-line connector I'm using for the cooler and dew heater so I think I'll find something better.

True!! I've found the same. Though I haven't been to either lately. We used to have a cheap shop in Honiton called Rainbows that sold timber amongst all sorts of other useful stuff. The land they were on got "obtained" by Tesco who wanted to put a huge supermarket on the site but never got planning permission due to local protest.

Same here!! A long hard day's work even with an electric mixer, pouring my block and pier!! I shall never forget that! ? The six support blocks for the building were a lot easier and could be done one at a time. I rather like working with wood.

There's usually a layer of micro-lenses then the Bayer layer. Below that is the sensor itself. It's all too easy to go to deep and destroy the sensor. Be very careful not to touch the blue surround. And especially the very fine gold wires round the outside. Break one of those and the sensor is dead! Good luck ?

Oh yes, we're always complaining about the weather - a truly British occupation ? I try to do astronomy and it's cloudy - I try to make a nice garden and it's too dry!! Sometimes I think I can't win. Doesn't really bother me much though - if I can't do one thing I do another. So I'm now working on astro stuff - specifically my all sky camera which was working but stopped last night. I also need to find out why my mount isn't working so I can do some Ha solar.