New control panel
Full house this week, albeit L had an early appointment elsewhere.
We had realised that the donated box had a sloping top, which wouldn't work in all of the positions we intended to use the panel i.e. at the front, for workshop operation, or rear, exhibition use. Stephen set about cutting the box edges level. Meanwhile, Geoff made up his preferred design of tag strip to join the loom and panel wiring. Brass nails in a strip of plywood.
First, the loom wires were fed in through the hole in the box base. But then a decision was required as to how to lay the wires out. It's not often you see the 'group leader' stretching his grey matter to the limit, but John's wiring system did the trick.
We also discussed the brilliant solution Geoff had conjured-up to control two points, sequentially, with one switch. More importantly, would we use it? It was considered that to have one set of points controlled differently to the others would require a different switch layout, which could cause confusion in the future. It was decided to adopt the standard format - one-switch-per-point, which required an extra wire in the loom, which Stephen fitted. There was one spare pin in the board connector, so not a problem.
We had decided to create a temporary panel-top, to test the new switches and knobs. Geoff had prepared and printed a layout, which was glued to a piece of hardboard. Geoff drilled the holes and Laurence then populated them with switches.
The old toggle switches were used for the sections, but temporary 'birds beak' knobs were used for the points.
Recap - Instead of the stud contacts used for solenoid control, we now needed to change polarity so DPDT switches were required. We had copious rotary switches that we could use, but the operating angle was quite small. Stephen had been researching alternative switchs and found one with a 45 deg. movement. However, it wasn't available in DPDT. When no alternative was found, we decided to use the ON/OFF switch in conjunction with a relay, to provide the polarity change. Geoff had suddenly realised that he had several of the switches and dug them out - perfect! What was even stranger was that the switches were identical to those in John's original control panel - spooky?
Knobs - we had the ubiquitous 'birds-beaks', but Stephen and Geoff wanted something different, something asymmetrical with a point/indicator at one end and no overhang at the rear. Stephen had researched knobs and circulated his preferences, together with designs for home-made units. Geoff had even fabricated his own idea in brass, which was tested today - the switch and knob/bar worked well. However, Stephen's continued research had produced a small knob made for guitars/effects boxes - not a bar, but a circular knob with white-line pointer that (somehow) had the same effect we sought. A mock-up of the size (19mm dia.) was played with and agreement given for Stephen to purchase some for testing. Watch this space...
Homework
Geoff continued with the wiring, completing both loom and panel elements. We think he's done this sort of thing before.
Stephen completed manufacture of the relay boards - one relay per point. There are three boards to allow for fitting in the box. A three-wire bus-bar loops through the boards - a 1.5v supply for the motors and the common return to the rotary switches. The feeds go straight to the relay.
This is the unit used to provide the 1.5v dc supply. We are using them for a number of applications on the layout as they are cheap (eBay / China / Hong Kong), and provide a regulated voltage.
LM2596S Step Down Adjustable Power Supply Module Input 3V-40V Output 1.5V-35V
