Electronics conundrum.

bricol · May 30, 2024

ajlelectronics said:
I have a (used to be) cheap and quite nasty aerial rotator. The controller to activate the motor is a triumph of cost saving and uses plastic gears on plastic shafts. Fairly quickly it all wears out and I have already printed a couple of new gears for it. This time it's terminal and so as they are impossible to find, I decided to build an electronic version in the old cabinet using the original transformer.

The original method of operation is very dirty... The motor in the rotator head is synchronous, meaning that it is locked to the frequency of the mains. There is a matching motor in the controller head and it is geared to drive a pointer.

To calibrate, one drives the motor until it stalls, then drive it the other way until it stalls. That is "synchronisation". It works but it is very much chewing gum and string. There is no actual feedback of any sort.

Exactly what we do we do with 16 motors on a nearly £3m machine. Well nearly - the motor gearbox units have good torque output - supposed to trip on excess current, but first the excess current has to be calibrated . . . one bent to bug gery few thousand quid drive mech and our sparkies had their answer to "have we set the current low enough?" . . .

I got the job to spec an overload clutch coupling to fit in the same space as the existing coupling for the next test run :thumbup:

Robotstar5 · May 30, 2024

bricol said:
Exactly what we do we do with 16 motors on a nearly £3m machine. Well nearly - the motor gearbox units have good torque output - supposed to trip on excess current, but first the excess current has to be calibrated . . . one bent to bug gery few thousand quid drive mech and our sparkies had their answer to "have we set the current low enough?" . . .

I got the job to spec an overload clutch coupling to fit in the same space as the existing coupling for the next test run

We used Rimostat couplings on our transfer lines, quite compact units.

bricol · May 31, 2024

Robotstar5 said:
We used Rimostat couplings on our transfer lines, quite compact units.

Used Mayr - UK agent is local, helpful and friendly. Not had any problems with them that weren't rapidly sorted in close to 30 yrs, including those of our own making.

ajlelectronics · Jun 1, 2024

Busy prototyping and trial fitting. Still some adjustments to do.

ajlelectronics · Jun 1, 2024

ajlelectronics said:
This is what is going into the original case...

View attachment 451466

I keep looking at this whilst drawing it up on EasyEDA and it seems a bit poorly thought out. Various issues with it...

The current sensor will only work in one direction. Seems a bit daft when timing could be established both ways.

The 7805 is going to run pretty hot, (I have a switching version going in anyway).

I can't work out why he felt the need for an opamp to drive the Arduino? The device (as a module but still no opamp) is designed to drive the analogue input without any other buffer.

The 2016 display can be simplified by running it as I2C. However I may go OLED once it works. It would look better in the old case anyway.

Relay modules are bit pointless, I have buckets full of 2N3904 transistors.

It has thrown up a connection difference, it seems that common on my motor is number 3.

The software is in two separate loads, which will be awkward for a quick calibration run; I think I will just be writing my own software.

ajlelectronics · Jun 5, 2024

A little progress, LCD wired and tested for operation with the I2C backpack. Some more wiring to do and a fair bit more tweaking of software to do when I have time.