As a change from printing lots of test pieces with no practical value, I thought it was about time I made something useful. I’ve given step by step instructions and a list of materials in case anyone else want to make any of these.
My wife has a growing collection of miniature glass and plastic Christmas trees (one or two of which I have made using Taulman T glass) which come out every year. They look more effective when lit from below so we have one or two of those led stands that one can buy. The trouble is, some of these ornaments are plain glass and look best with coloured light while others are already coloured so look best with white light. The other issue with some of the stands one can buy is that they take those really small button cells which make them expensive to run compared to using say, rechargeable AA or AAA batteries. So I decided to make some that would take rechargeable batteries and that could be switched between colour changing or white.
Initially, I had planned to use rechargeable PP3 9V batteries. These would have been easier to fit inside the base and would have meant that I could run 2 or 3 LEDs in series with a single current limiting resistor. However, when I looked into the capacity of these batteries, the amp hour rating is very low which would have meant that they would only have lasted about 8 to 10 hrs between charges. So, I decided to use AA size cells instead, which have a much higher capacity. The voltage drop across the super bright white LEDs is 3 volts and for the colour changing it was 2.4 volts (variable depending on which colour is being produced) so I needed at least 3 batteries to give me 4.5 volts and the LEDS would have to wired in series, each with it’s own current limiting resistor.
The colour changing LEDs are not as bright as the white LEDs so I decided to use 4 colour changing ones and 2 white ones.
In addition to the LEDS, I also needed a switch. I had hoped to use a miniature ON-OFF-ON slide switch but was unable to find one. The best I could find was On-On which would switch between colour changing and white but had no centre “OFF” position so I ended up using two switches. One for ON-OFF and the other for Colour – White. If you can find an ON-OFF-ON version, it would simplify the wiring quite a bit.
Then I needed clips to hold the batteries and provide electrical contact, some wire and some strip board.
The complete list of materials for one of theses stands is as follows.
2 off super bright white 5mm LEDS (one could also use 3mm)
4 off slow colour changing 5mm LEDs (or 3mm)
1 off piece of strip board 25mm x 25mm
3 off Keystone AA (-ve) contact part No 209. These are the dimensions
3 off Keystone AA (+ve) contact part number 228 as below
2 off switches PIC part number SS-22f25-G dimension as below
Printed parts – Base, Top and Insert. These can be found on Thingiverse here Printed parts files
The first thing was to make up the strip board LED modules. Each LED has it’s own current limiting resistor, the value of which will depend on the specification of the LEDs. In my case I used 220 Ohm and 180 Ohm. The +ve input to all 4 of the colour changing resistors are connected together as are the 2 +ve inputs for the white resistors. The -ve side of all the LEDS are connected together. Here is a picture of one of the made up boards.
The 4 colour changing LEDS are on the outside and the 2 white ones are on the inside. The red wire is the +ve for the white LEDs and the Orange is the +ve for the colour changing LEDS. The black wire is the common -ve.
A quick note about using these slow colour changing LEDS. When they are first turned on, they are all the same colour and start to slowly fade to the next colour. However, they don’t all change at the same rate. So after a period if time they get “out of sync”. This results in many more combinations of colour which are more subtle than just RGB and in my opinion, give some quite pleasing effects.
The next thing was to design and print the base which holds everything together. Here is one of those bases.
And here is one with everything wired up.
The pictures should be self explanatory. The base is designed to take the switches which are a snug fit but slide in from the top. The clips for the batteries are a press fit from the top. NOTE, solder the wires to the clips before fitting the clips otherwise the heat will melt the plastic. The lower right hand battery clip is the +ve terminal which goes to the centre terminal of the ON-OFF switch which is at the top. One side of this switch goes to the centre terminal of the changeover switch which is on the right. The red wire from the LEDs goes to one side of the changeover switch and the orange wire goes to the other side of the switch. The black -ve LED wire goes to the -ve battery clip which is the top right one. The batteries are then connected in series -ve to +ve as shown by the blue wires. As I mentioned before, life would have been a lot easier if I could have found a miniature ON-OFF-ON switch rather than having to use two ON-ON switches.
Here is a finished base with batteries installed. For testing, these are just ordinary A batteries, not rechargeable. The LED board sits in a recess but I used a couple of spots of silicone sealant to hold the LED board in place (but any glue will do).
I forgot to take a picture of the top but here is an image from OpenScad
It is designed to just clip on and has 2 “prongs” which locate it and also hold the switches in place. The rectangular cut out takes a clear insert which I printed separately.
I printed the inserts using Taulman T glass clear. They simply press in and I used some clear silicone sealant to hold them in place. Here is a picture of three of them.
I actually made 10 of these. One was a working prototype so “er in doors” has 9 useful ones.
Here is a picture of one of them in white. The featured image at the top shows it in colour mode. Sorry about the reflections of my window blind which show on the top but you’ll get the idea.
I put all the files including the OpenScad file on Thingiverse so you can play around with the design as you see fit – maybe you’ll be able to find an On-Off-On switch to simplify things. Here is that link again Printer parts files