How to assemble a Radio Control Electric Switch

This switch is quite simple but has some great features and worth a try. All of the parts are readily available from most electronics stores or if you tinker with electronics a bit you may have them in your junk box as odd spares.

How to make the printed circuit

Board as it is so easy and is a rewarding experience to complete the whole job yourself. There are no suggestions of how to mount the switch.
As you can see by the photo, didn't put it in a case as it would just add weight and  can't see why it would need it if you can have it held by foam rubber. I cut a cavity out of some foam and wrapped a rubber band around it all.
The relay is mounted away from the circuit so the motor current has less effect and cause glitches and mounted with double foam tape.T the relay away from the board to keep electrical interference to a minimum.
The circuit doesn't have to be made like this as you could have a go at building it up on a veroboard but I do find it a fair bit harder, somedon't. It is a bit bigger than it's commercial counterparts but this is as small as I think most people can go with an ordinary soldering iron and tools.
A 6v relay seems to work fine even though the receiver voltage is only 4.8v. There are no pads included on the P.C board for the switching side of the relay as it depends on what sort is used. Be sure to find one that can handle the current that is put through it and do a good job of the soldering as there is a lot of vibration in a model aircraft. A double pole relay can be wired to short out the motor when power isn't on so a folding prop can stop rotating and fold properly. See diagram. Adjust the trim pot so that the relay turns on at the desired position of the radio stick.

Note: there is a slight delay in switching.  You can get a receiver plug by buying a servo extension lead and cutting it to the desired length.

To make the Printed Circuit  Board

Things needed

Blank board copper on one side. (Fibreglass is preferable but the older bakalite type material is ok. It fractures easier though)
Dalo pen
Ferric chloride (You can get it already as a solution or as powder and mix it yourself. Read the warnings about it's corrosive properties as you may end up with no sink pipes.)
Carbon paper (The same sort of stuff that you get in receipt books etc.)

Draw out diagram by placing the carbon paper onto copper face and the master on top. Then fill in the tracks you've drawn onto the copper with the Dalo pen. Cut board to size & put in Ferric Chloride till excess copper is etched. You could warm up the ferric chloride to make it work a little quicker. Swish the solution around a bit to keep fresh solution up to the copper. Wash & clean up then drill holes. The holes are quite small and you may need to but that size drill at an electronics store as well. Centre punch the
holes first makes it easier to drill.

See the prototype

You may need to obtain a chart that shows how to orientate the transistors the right way. In the diagram there are markings for each leg as B,E,C which is base, emitter and collector. These have to be the right way round and as they vary on different transistors of the same sort you'll have to do some digging yourself or as the supplier of the parts.
The Integrated circuit the electrolytic capacitor and the diode are the other three parts that must go the right way. The IC usually has a notch or similar at the end that corresponds with pin one marked on the diagram.

The diode has a black band at one end and that also can be seen on the diagram. The capacitor usually has negative or positive marked on the case and you'll see the + marked on the board diagram.
The trim pot RV1 uses only the middle and one outside leg. Just bend the other out of the way.
To find the way to wire the receiver plug, look on your servo wires and see if there is a red, black and another color wire as it is probably red for positive, black for negative.

Layout and print details