Difficulty Operating Solenoids with an Arduino Uno

I got the box for my Milling Machine Table Drive from Farnells at a very good price, I think they are end of line, see my post under workshop progress 2020 August sometime

Thread drift (again) but analog meters like the AVO 8 (I have the GPO version of the SEI Selectest Super 50 which is similar) do have a couple of advanages that have not been mentioned:

They are good for assessing changing voltages because A. they average faster changes and B. your eye and brain can average slowly changing ones. DMM just give random numbers.

They are good when making manual adjustments o circuits. The visual feedback is almost immediate.

Some DMMs have bargraph displays that help in these situations but the implementaton and usefullness varies considerably, even from good manufacturers. Quite a lot of digital power meters and the Fluke 8920 TRMS digital voltmeter still have analog displays to assist with adjustments. Have more digital meter than analog but there is still a place for both in a well equipped workshop. If the only choice was the quality large scale analog like an AVO 8 / Super 50 or a cheap ebay/maplin/screwfix DMM I'd take the analog everytime.

Note as well that the midscale accuracy of the AVO / Super 8 is similar to a basic 31/2 digit DMM.

Robert G8RPI

I have sent yo a private message.

James.

John.

I am a way off from starting the clock itself as I am still vacillating over the design. However, I have programmed six pins on the Uno to operate at different intervals. One will operate each second, one each minute and one each hour. A fourth will be used to strike the quarter hours, a fifth to chime the hours and the last one will mark the days. I have used a RTC to ensure that it keeps proper time and it has a LCD display to check the time.

Mechanically, there will be a lifting solenoid connected as the load on each transistor. This solenoid will pull a lever which will advance the hands, strike the hours, ring the chimes and mark the day appropriately. This stage is well in the future still.

Regards,

James.

Out of curiosity I looked up what sort of digital multimeter you could get for the new cost of an Avo8. In 1953, the latter was advertised at £23.50, equivalent to about £660 today. (Source Richard's Radios)

Today, that money would get you a calibrated 5½ digit Siglent SD3055 Dual Display bench multimeter (DC voltage accuracy 0.015% of reading per year and 0.003% of range), plus many other goodies and change.

Not tempted - my ordinary Maplin analogue and basic 3½ meters do all I need, and I occasionally roll out the Avo too.

Dave

Thanks James, so the relays are just representing the solenoids?

I don't know if you're familiar with the old Synchronome clock which used an electromagnet driven ratchet motor to operate the dial impulsing every 30 s with a very audible clunk. In the case of the observatory version it clunks every second, and every 30s too. Also the master clock clunks every 30s as the impulse is delivered to the pendulum. In my version of the Synchronome the original EM drive to the dial was instantly vetoed by the domestic authority because of the noise, so I converted the dial mech to use a small stepper motor instead to drive the minute hand. The dial is now virtually silent in operation.

This might be a point to consider - stepper motors can be cheaper than solenoids and at "clock" speeds virtually silent.

John,

I confess that I have used relay and solenoid loosely. Originally, I was going to use realys, but then looked at the type of solenoid which has a sliding plunger to push or pull the mechanism. My wife's comments when I had it running with just one such solenoid made it clear that alternatives would be needed due to the noise. I have now settled on the type of solenoid which is just a round electro-magnet without any form of plunger or arm. I propose to design and build a mechanism which retains a tiny air gap between the face of the magnet and the activating arm to avoid noise.

I toyed with the idea of stepper motors, but I really like to the idea of a clock with lots of levers and arms rocking away. It might all prove to be unworkable, but I shall give it a go.

We used to have synchronised electro-mechanical clocks at the telephone exchanges where I worked. I cannot recall the make or any details, other than that they were not exactly silent.

Regards,

James.

Aha! They would be PO Type 36 clocks! More details here. Very collectable these days. Based I believe on the Gents Pulsynetic system. I worked for the PO in the last days of Strowger and I guess the noise of the switching more than drowned out the noise of the clocks!

Do you mean a rotary solenoid? I have thought of using those but not found a cheap source and they don't look easy to make.

John,

Like you, I worked in the old Strowger exchanges in the later years, moving into "traffic" in 1986. They were noisy places. I am sure that my hearing was dulled by the constant racket.

This is the type of solenoid Lifting Solenoids which I plan to use. I bought one from e-Bay as an experiment and have found someone in this country selling five more unwanted solenoids for a very reasonable price.

Regards,

James.

I only had to visit them as I was in research but spent some weeks out in Gloucester area on training, of which the most interesting bit was going out in vans with the installers or in the exchanges trying to hear a TO explaining how a register-translator worked - fascinating!

PO type 36 was a Hipp clock, so nothing like as noisy as a Synchronome. Confusion arises because the GPO owned the design (I think) but had them made by several manufacturers, Gents included

PO36

Type 46 was similar but had 1/2 second pendulum, much rarer

That takes me back, somewhat.