Gina

The teeth on the 64 tooth ratchet wheel seem rather small with 120mm OD as fits nicely in the clock case so I'll have a rethink. Could use 32 teeth and 4:1 motor to crank wheel.

Think I might wear a hard hat when working on the observatory!

The 125mm ratchet wheel might work with a gear on the 8t sprocket with 50 teeth or more. Need to do some calculating do see if this would be viable. 8t sprocket want to rotate at 400s/rev. Motor shaft rotates at 200/256s/rev = 400/512s/rev This makes total reduction required 512:1 This is purely a power of two so ratios of 5:1 are out it seems. No problem, just need to design and print new ratchet wheel and gears. I think this can be achieved with a spur gear on the 8t sprocket and matching ratchet wheel pinion. 8:1 gear ratio and 64 tooth ratchet wheel. This assumes the pawl works directly off the motor shaft but a 2:1 reduction gear would make the sprocket to ratchet wheel ratio a more manageable 4:1

I have some ratchet wheels from previous versions with 50 ratchet teeth and 10 tooth pinion. Smallest is 125mm OD which is a bit big. Here's a photo of the current state of the clock. To get an idea of scale the chain wheel is 125mm OD.

If I were to use the same stepper motor for the auto-winding as the pendulum drive the above will need modifying, viz. The centre wheel turns once per hour so the drive sprocket 4 times an hour or 15m per revolution. Chain drive sprocket has 18 teeth and motor sprocket 8 teeth. Motor sprocket wants to turn 18/8 times in 15m or 18x4/8 = 9 times an hour ie. 9/60 = 3/20rpm or 20/3 mins/rev which is 20x60/3 = 400 secs/rev The crank gear runs at 2s per rev so the drive would want reducing by 200:1. Seems this calls for a ratchet drive system like I used before. Not a 200 toothed wheel though!

It would be helpful if I can drive the auto-winding from the same motor so the next thing is to look at the calculations.

This is all that's now required in the sketch and in fact, I don't think it needs either the Serial Monitor or to get the time from the RTC module. I shall try it without and leave just the square wave setting. // Filename :- Pendulum_Clock__v5_with_NEMA14_Auto-winding_29_10_2019 // #include <DS3232RTC.h> //http://github.com/JChristensen/DS3232RTC #include <Time.h> //http://www.arduino.cc/playground/Code/Time #include <Wire.h> //http://arduino.cc/en/Reference/Wire (included with Arduino IDE) // String VerString = " Pendulum_Clock_v5_with_NEMA14_Auto-winding_29_10_2019"; // void setup() { Serial.begin (9600); // Enable Serial Monitor via USB Serial.println(VerString); setSyncProvider(RTC.get); // the function to get the time from the RTC if(timeStatus() != timeSet) Serial.println(" Unable to sync with the RTC"); else Serial.println(" RTC has set the system time"); RTC.squareWave(SQWAVE_4096_HZ); // 4096Hz square wave } // End

I've decided to drive the pendulum rod just below the clock face. This will consist of a cross-bar connecting rod connected to an offset (crank) bearing on a 64t gear. A stepper motor will drive this with a 25t gear arranged to drive the pendulum at 2s per cycle. The electronics will consist of a Real Time Clock module (extremely accurate) driving a TMC2100 stepper driver module. The latter can provide very quite stepper motor operation (I'm Using one in my Giant 3D Printed Wall Clock). Pulse rate from RTC = 4096 Hz square wave NEMA14 stepper motor has 200 full steps per revolution Microstepping multiplies this by 16x Gear ratio to crank is 25:64 step down. --- Now to the calculation --- 4096/16 = 256. Equivalent of 256 full steps per second. Seconds per revolution of motor shaft = 200/256. Seconds per revolution of crank = 200/256 x 64/25 = 200/25 x 64/256 = 8x64/256 = 2 Here's a quote from an earlier post with an Arduino sketch. I can modify this and drive the TMC2100 directly from the RTC module cutting out a number of lines of code. The Arduino would only be needed to set the parameters in the RTC module.

Well done. Coming on nicely

Oh dear!!! That doesn't sound very good news for when I resurrect my weather station project. Hope you can get it sorted out, James. Good luck. Actually, thinking about it, I have a slightly different setup with an Arduino Uno and shield. The Arduino acts as the 1-wire controller.

Lovely and well deserved IMO.

Just seen this - what a shame!! So sorry for the organisers and all the work they put into these events. I wasn't going as I'm not up to travelling far these days but have great sympathy for those who were going.

Having another look at this project. The impasse ATM is the escapement. To date I have not been able to produce an accurate enough escape wheel. I've worked out that the tolerance required is of the order of 0.1mm and have found this difficult to achieve in a 3D printer. I may have another attempt with my latest 3D printer. The problem is that if the teeth are not all exactly the same distance from the centre of rotation and the same shape, the drive is either insufficient to keep the pendulum swinging or the escapement "skips". One "fudge" I've thought of is to drive the pendulum separately so that the escapement is not required to drive it. This would mean a far lighter weight would be needed to run the gear train with less tendency to "skip". Of course, the pendulum would need to be "tuned" fairly accurately to the 2s period of the drive or the two would "fight". Effectively, the pendulum is a very high Q tuned circuit, albeit a mechanical one. Apart from getting round the escapement problem, the clock would effectively be a "slave" to the RTC module and stepper motor driver circuit. I had planned to add an automatic time-keeping system whereby the pendulum length was adjusted to make the clock keep time. A closed loop control system. The open loop pendulum drive would be simpler. I want to get the time-piece part of the clock working so that I can get on with the striking mechanism which intrigues me.

Water cooling might seem OTT but it's much easier that blowing air out of the observatory up to the ASC. Just a couple of small pipes to go from inside to outside and there's already a gap under the barge boards where they can go. Also, it makes the enclosure much easier to seal to keep damp out.

The water in the reservoir is tepid so several degrees above ambient and I could make the cooling better with a 120mm radiator and fan. I have both but the smaller radiator is easier to fit inside the ROR. I'll try that and upgrade to the bigger one if wanted.

Returning to camera cooling, the water cooling is not working as well as the fan and Artic big heatsink but with nearly 20°C below ambient of cooling I think it should be adequate and no need to cut a big hole in the side of the ROR.

Yes, I plan to go for 1.75mm filament except for my Giant printer which will be using 2.85mm. Next colorFabb sale I shall buy more 1.75mm filament, PLA and PETG white. The other reason for interchangeable nozzles is to be able to change nozzle size without messing about with a hot block to change nozzles.

Camera sensor temperature now 1°C. Peltier TEC is drawing 2.6A at 13.8v.

Now have the water cooling system set up on the table and running a test. Ambient temperature 18°C.

My interchangeable hot ends consist of Precision Piezo Z probe unit, cooler, heater block with heater and thermistor plus 4 wire connections. To swap I remove the 4 screws from the front of the E3D Titan extruder and swap hotend plus filament guide. Not quite as easy as Chris's system but best I could manage with what I have.

There are drips of blood on the floor of my observatory!!

Finished and cooling.

+1

Wasn't getting very good results with the 0.8mm nozzle and 2.85mm filament so swapped hotends to the 0.4mm nozzle and 1.75mm filament version. Then for better interlayer adhesion to ensure a watertight reservoir, I went for PETG. The reservoir is now printing nicely though taking a while. Interchangeable hotends certainly helps. My thanks to @Chriske for that idea.

Small (80mm) water cooling radiator for my ASC camera cooling system. Already had an 80mm fan. This shows the two side by side. A normal 120mm radiator would have been overkill.