Building a rotary switch with push button (English).
J. Pedro Bibiloni. Translation by Manolo Hdez-PeñaLopez Muñoz
AIM OF THIS TUTORIAL:
This tutorial shows how to build a rotary switch including a push buttom in the centre of the knob; this switch will control some simulators functions through the IOCards designed by Manuel Vélezhttp://www.opencockpits.com This type of switches are mainly used in the EFIS panels.
|Note from the author: Stages 1 to 4 are just the same as the ones described in the concentric rotary switches|
1. TAKING ROTARY SWITCH INTO PIECES
Lightly force the plastic hooks (be careful not to break them). Open it being cautious with the metallidc balls and spring inside the switch (the balls can be thrown really far away by the spring, far enough to loose them forever). Take apart these pieces for later. Also apart the metallic contact that closes the circuit; take into account the initial position for this piece.
2. ROTARY SWITCH AXLE REPLACEMENT
Using the wood sheets saw, cut the plastic axle leveled with the switch body.
Then put a mark in the centre of the axle and drill a 6 mm. hole (is better doing it by steps, 4 mm. first, then 5 mm. and so on). Cut the aluminium pipe to the desired length (main body + fitting screw + knob) and glue it into the hole. You can sand down the parts to glue, they will make better contact if you do so. Now we have to cut the inner spring and to drill the bottom body of the switch.
3. CUTTING THE INNER SPRING
We have tu cut the spring into two pieces. The length of each part is more or less: (original spring - aluminium pipe - ball radius) / 2. It isn't an exact formula, so it's better not cutting so much the first time and adjust in several cuttings.
4. DRILLING THE BOTTOM BODY
Drill a 5 mm. hole just in the centre of the bottom body, as shown in the picture. This hole must to be centered with the 6 mm. pipe previously glued.
5. ASSEMBLING THE SWITCH
We are ready now to assembly all the parts. Be careful with the small parts as balls and springs. Test the correct switch operation. If you think the strenght is not the correct one (consider that in the real airplanes, the strenght is enough to avoid the rotary encoders move with the plane vibration), cut the springs a little more.
6. BUILDING THE PUSH BUTTON AXLE
Cut the screw head (Why DIN 931?: because the thread is only part of the screw so the flat part will move easily through the 6 mm. pipe). Total length of the screw must be= rotary switch lenght + knob + distance between rotary switch and push button (the last to confirm later).
7. PLACING THE PUSH BUTTON AXLE
Glue the M-4 bolt on the push button. Keep the thread clean of glue.
8. DEFINING THE LENGHT FOR THE PUSH BUTTON AXLE
Cut 20 mm. of squared aluminium frame. Drill two 10 mm. lined up holes at opposite sides of this piece. Fix rotary switch in the upper hole and push button in the other (in my case I have made a big drill for the push button due to its size). Once both elements and the knob are fixed, screw the unheaded screw in the bolt. We can now check the lenght of the inner axle taking into account that we have to glue a little circle of rigid plastic on the top of this axle. This circle will fit in the knob so we will press over it and the inner axle will transmit the pressure to the push button. We can letter this plastic with the button function.