No I dont have a DMM but I think that will be the next purchase and a soldering iron

Good investment if you want to dive deeper into electronics. Recommend one of the Fluke models.

 

Good investment if you want to dive deeper into electronics. Recommend one of the Fluke models.

Yes I'll definitely have to get one, might order one later

So, thinking about my little project, I'm confident that the circuit is correct now, and I'm actually thinking of using the original 24V bulbs, but my next problem is adding some control to it.

I'd like to add a 3way switch - 1 position which be off, 2 position would be for it to be controlled by a button, 3 would be to be controlled by a motion sensor.

Is this possible? I can think of loads of questions, is there a particular rating the switch has to have? I'm thinking of using an old cool looking aircraft switch, but not sure if this is possible, and also how to facto in these controls into my circuit.

Sorry for the long post

 

Is this possible? I can think of loads of questions, is there a particular rating the switch has to have? I'm thinking of using an old cool looking aircraft switch, but not sure if this is possible, and also how to facto in these controls into my circuit.

Just about anything you want to do is possible. Just a matter of how you go about doing it. If you return to 28 volt aircraft lamps (327 bulbs) or use LED newer substitutes (expensive) it becomes a matter of exactly what patterns you want and exactly what sequence you want. You can use discrete components or even a uC (micro-controller). Most 327 28 VDC aircraft lamps (indicator type) were driven using 2N2222 transistors but also as you can see Darlington pairs like you have also work. So just a matter of mapping out what you want and how to get there.

Ron

 

Yes I'll definitely have to get one, might order one later

So, thinking about my little project, I'm confident that the circuit is correct now, and I'm actually thinking of using the original 24V bulbs, but my next problem is adding some control to it.

I'd like to add a 3way switch - 1 position which be off, 2 position would be for it to be controlled by a button, 3 would be to be controlled by a motion sensor.

Is this possible? I can think of loads of questions, is there a particular rating the switch has to have? I'm thinking of using an old cool looking aircraft switch, but not sure if this is possible, and also how to facto in these controls into my circuit.

Sorry for the long post

One way to implement this type of functionality is to send the switch position to your Nano along with the push button and motion sensor. Then implement in code whatever you want. This has the advantage of increasing possible flexibility while keeping the circuitry simple and straight forward.

 

There is one "little" caveat for switches and relays that you learn the hard way. Well, in my case I had to deal with pA of current or 10e-12 Amps. That world is different as is 50-3000 Amps.

There is a specification for a switch or relay called "wetting current". The is the current necessary to keep the contacts "clean".
There is also "switching current" or how much current can be switched. And whether the current is AC or DC.
There is also for some switches a "HP" or horsepower rating.

10 mA is a good rule of thumb for wetting current. Precious metals can reduce this. Back in the day "mercury wetted" relays were sometimes used.

Relays can sometimes be put in a category of "Definite purpose contactors". e.g Motors, lighting or RF.

Had these high voltage SPDT relays (40 kV at 2A) that had to switch at 0V.

There is a category of relay that you may want to be aware of is the "magnetic latching relay" They usually come in single coil and dual coil and operate with a pulse. The permanent magnet is not enough to keep the contact in position. but can hold it in position.

In the single coil variety, you have to reverse the polarity of the coil. In the dual coil variety, you have two coils caled set and reset. These need to be DC.

I won't really cover it, because they are big and rare is an "impulse relay". Every pulse is a different position. It wa show old telephone switches were made.

This is really a lesson in reliability.

==

The other comment I want to make is that contacts "bounce" when you use them as inputs to micocontrollers and IC circuits.
They take time to settle so the processor sees a random number of state changes. Another topic to read about.

 

As was already mentioned, the most obvious and flexible way to make your switch operate is just use it as an input to the MCU, then have your software do whatever you'd like based on the state of the switch.

This would even let you do something like make the switch behave differently if it was operated while the button was held down, or other creative things.

Such a switch will only be handling 3.3V or 5V at very low current so literally almost any switch will do. You might be able to find a surplus aircraft switch of the same vintage on eBay or from a similar source.