looking for screw switches

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vk2icj
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looking for screw switches

Postby vk2icj » Sat Feb 21, 2015 5:26 am

Hi All

Last minute bits for Thunda. Looking for an Australian supply of Screw switches that are suitable for turning on my altimeters/trackers. I have a minimum diameter 54mm bird I'm putting together and my switch isn't going to work without modifying the entire ebay. I need something small and reliable.

Cheers

Chris
73 de vk2icj ..

TRA #4948

matthew
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Re: looking for screw switches

Postby matthew » Sat Feb 21, 2015 4:20 pm

I've wondered why Blake doesn't sell them, but I suspect it's because they aren't hard to make. Just glue a nut to the other side of the board and put two contact points where the screw can bridge them.
Matthew Small
AMRS #33 L3
TRA #11466 L3
QRS #133


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air.command
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Re: looking for screw switches

Postby air.command » Sun Feb 22, 2015 4:39 pm

vk2icj wrote:Hi All

Last minute bits for Thunda. Looking for an Australian supply of Screw switches that are suitable for turning on my altimeters/trackers. I have a minimum diameter 54mm bird I'm putting together and my switch isn't going to work without modifying the entire ebay. I need something small and reliable.

Cheers

Chris

Hi Chris, I normally just make my own. Get a double sided PCB, drill a hole in it and then solder a brass nut to one side. On the other side use a larger drill bit to trim away the copper a little from the edge of the hole. I then usually tin the copper around the hole for the screw head to sit on. A thicker layer of solder allows the head to make really good contact when screwed down. I normally just find an old computer PCB that has large ground planes on both sides and cut that out. You can then drill a couple of mounting holes either side. I normally cut the copper on both sides between the screw and the mounting holes to make sure they are electrically isolated. I am using these in my project as well.

- George
Crop Circles: ... just a bunch of guys looking for their rockets ....

natty
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Re: looking for screw switches

Postby natty » Wed Sep 23, 2015 5:04 pm

Hi George,

Can you post some pictures of your switches?

Cheers
Natty
L3
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air.command
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Re: looking for screw switches

Postby air.command » Wed Sep 23, 2015 5:58 pm

Hi Nat,

Here are some pics of the screw switches.

The screw itself is a brass 1/8" machine screw. But an M3 or an M4 would be fine. As mentioned above I put a few blobs of solder around where the head of the screw goes so that it makes good contact when you screw it down. The size of the PCB in these photos is 8x25mm

Top view:
screw_switch1.jpg
screw_switch1.jpg (103.52 KiB) Viewed 1182 times


screw_switch2.jpg
screw_switch2.jpg (91.67 KiB) Viewed 1182 times


Bottom view:
screw_switch3.jpg
screw_switch3.jpg (82.79 KiB) Viewed 1182 times


Here is a more detailed view with the screw removed. It's hard to see in the photo so the red circle shows up to where the copper has been removed from around the hole. The white marks on the inside of the circle is just the fiberglass. You can see where the screw head has bit into the solder near the wire.
screw_switch4.jpg
screw_switch4.jpg (149.81 KiB) Viewed 1182 times


To mount it I drill a bigger hole in the bulkhead so the nut and wire can fit and then two smaller holes for mounting screws.

- George
Crop Circles: ... just a bunch of guys looking for their rockets ....


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