Advice for buying rotary switches?

[BlownUpCapacitor]

Hi, I am looking for advice on the sourcing of rotary switches, specifically 12 position dual decks, and an 18 position quad deck. I need these for a future project I want to work on.

The main problem for me is my budget constraint. I don't want to spend $100 a piece for a single rotary switch on digikey. I was looking at ebay, but they don't have them.

I could use a uC and some relays, but I feel like nothing beats a good old fashioned rotary switch. Thanks.

[PCB.Wiz]

Hi, I am looking for advice on the sourcing of rotary switches, specifically 12 position dual decks, and an 18 position quad deck. I need these for a future project I want to work on.

The main problem for me is my budget constraint. I don't want to spend $100 a piece for a single rotary switch on digikey. I was looking at ebay, but they don't have them.

I could use a uC and some relays, but I feel like nothing beats a good old fashioned rotary switch. Thanks.

All of those requirements paint you into a corner.
Amazingly, I do find a 18 pos 4 bank switch listed on Digikey, at $226  1 unit in stock, marketplace.
So you can see they are rare and very expensive.

If you want the rotary switch feel, you may be best to approach from the other direction, start looking for ANY rotary switch close to your position count.
A quick scan finds 18 is rare, but Alps have a 20 position SRBM1L1400, they call a pulse switch, maybe quad coded ? you would need to get one to see what it actually does.
sub $10, so a good price.

20 positions also finds an unusual Grayhill 60A18-4-RAC - looks to be a 20 detent rotary optical encoder with joystick switches.
higher price, at $48, at digikey, but looks to be designed for human interface uses. Quite nice.

For $80, I see Mouser have a Grayhill 20 step, absolute gray encoder (wrong image) single bank.
Mouser also show bourns absolute encoders, sub $10, but 16 steps gray.  How important is 18 steps
There is a TT part code EN18ABHH22H0H0 for 24 step absolute, but no stock showing. (MOQ 720?)


Generic rotary encoders seem common in 18 or 20 PPR, some have push switch to select.  A small display could tell you where it was set.

[Benta]

12-position are pretty standard and should be easy to find.
But 18-position? I've never seen one in the wild. Custom designs for multimeter or something like that might have been made, I guess.
Perhaps you should rethink your design?

[BlownUpCapacitor]

The number of positions is not very critical for the quad wafer switch. I have a tolerance of 18≤positions≤22. My task is to design an analog oscilloscope for a school project. The quad wafers are meant for the time base, so naturally, the more positions, the better.

The 12-position dual wafer rotary switch on the other hand is not very tolerant to change. I do not want to go through the mess of finding a suitable attenuator design where I can fit everything in a compact space, whilst keeping functionality.

I'll look for other rotary switches such as ones with 20 positions.

Thanks for all of your help guys!

Side question: Where would I source an oscilloscope CRT, where it's not Ebay. I don't trust the sipping handlers to not break such a tube.

[themadhippy]

try looking at the diy hifi suppliers, for example a  24 way 4 pole switch for just under £30 https://www.hificollective.co.uk/switches/blue-4-pole-24-way-switch-gold-plated.html

[PCB.Wiz]

Side question: Where would I source an oscilloscope CRT, where it's not Ebay. I don't trust the sipping handlers to not break such a tube.

I've not seen those offered for a very long time ! You also need to generate the EHT, and for the better ones that's > 10kV ! Not so school friendly.....

Meanwhile, there are many kits using LCD displays, and the modern scopes use 800 x 480 or better LCDs and rotary encoder knobs for time base and attenuators.

Also, multimeters with scopes inbuilt are coming down in price, you can get a school suitable one for less then the cost of one of the mentioned switches !

Single channel 2.5Msps 4000 count : https://www.aliexpress.com/item/1005006514600341.html  ~ $41
Dual channel 280Msps 25000 count : https://www.aliexpress.com/item/1005006437581064.html  ~ $75  this ZT-703S is mentioned elsewhere on here.

and this mentions a new model again https://zotektools.com/news-with-zoyi/   "New Product Ultra-thin large screen portable oscilloscope multimeter series Coming soon ~~"

[BlownUpCapacitor]

I know HV is dangerous, but from my understanding, as long as it's been contained and isolated, it's not a huge danger. I myself have quite a bit of experience with repairing analog scopes. However, I know this is not a justification for potentially risking my life.

However, I am planning to just use some existing CRT driver designs so I don't have to fiddle with that part. Just the horizontal amp, sweep generator, trigger generator, vertical pre-amp, CRT vertical amp, attenuators, etc.

A personal project is something that every student at my school starts in freshman year, and finishes in sophomore. So it's not meant to be a single small project like building some cheap DUY DSO from Amazon. I actually have been wanting to build my very own analog oscilloscope since my early middle school years. I find this my chance.

Anyway, enough of my lore, I was thinking of perhaps removing CRTs from existing oscilloscopes? I have a local e-recycle that has quite a bit of 2225s from the local college, and a few more lesser-known brands that I don't even remember. What interests me is a Telequipment D54, I don't think the rest of the parts work, but I hope the tube is still good.

The problem is, would it be moral to crack open a perfectly good and useable scope and snatch its CRT for the sake of some HS project? (If the D54 has a bad tube)

There's a reason why I have experience repairing old scopes, even at a young age. I don't like to see fixable scopes going to waste.

[Martian Tech]

The number of positions is not very critical for the quad wafer switch. I have a tolerance of 18≤positions≤22. My task is to design an analog oscilloscope for a school project. The quad wafers are meant for the time base, so naturally, the more positions, the better.

The 12-position dual wafer rotary switch on the other hand is not very tolerant to change. I do not want to go through the mess of finding a suitable attenuator design where I can fit everything in a compact space, whilst keeping functionality.

I'll look for other rotary switches such as ones with 20 positions.

Thanks for all of your help guys!

Side question: Where would I source an oscilloscope CRT, where it's not Ebay. I don't trust the sipping handlers to not break such a tube.

CRTs (not cheap): https://www.surplussales.com/Tubes-Sock-Acc/CRTtubes.html
This may work for the switch: Tektronix 262-245 (from 545A oscilloscope) - 24 pos, $15: https://www.surplussales.com/Switches/SWRoMisc-2.html (scroll down)

[PCB.Wiz]

I know HV is dangerous, but from my understanding, as long as it's been contained and isolated, it's not a huge danger.

Generating it is not trivial, and certainly 'keeping it contained' is also challenging !

What interests me is a Telequipment D54, I don't think the rest of the parts work, but I hope the tube is still good.

I find this
https://antiqueradios.com/forums//viewtopic.php?f=8&t=370505&start=20
mentions about 3.5kV overall, so that's not the EHT of 100MHz levels scopes.
The blog there includes some upgrades....

[BlownUpCapacitor]

I found the tube datasheet https://w140.com/tekwiki/images/7/7e/Thorn_d13-47_crt.pdf and it says it can use a maximum of 7kV for acceleration. I was perhaps thinking -1kV at the cathode and 5kV at the anode for 6kV acceleration.

And yes, generating a high voltage for CRT use is difficult. If I can't manage to make my own custom one, I can simply just use the original CRT driver circuit of the D54. This was my original plan anyway.

This project isn't meant to be the creation of a super wide band scope like a Tek 7104, but just a learning project to create a useable scope up to maybe a few good megahertz.

Thank you for your advice.

Edit: New idea, if I really can't create my own complete scope, I guess I could just design some kind of plug-in for my 5110 or 7904. My e-waste center has plenty of TM500 and 5000, 7000 series plug-ins, so maybe I can find a faulty one and just use its housing.

[PCB.Wiz]

Edit: New idea, if I really can't create my own complete scope, I guess I could just design some kind of plug-in for my 5110 or 7904. My e-waste center has plenty of TM500 and 5000, 7000 series plug-ins, so maybe I can find a faulty one and just use its housing.

That could make more sense, plenty of interesting work in analog front ends (+ ADC's if you want to add a digitising to a LCD option)

These encoders looked nice, 20 clicks and a push switch, at 5 for $3.10
https://www.electrodragon.com/product/5pcs-rotary-encoder/

Another key feature you gain with encoders+electronic ranging, is you can add Auto-Set feature to the scope, makes it easier to use.


Addit: I don't think you need absolute encoder for a scope, if you display the settings, but I found some interesting ones under CTR brand
https://www.lcsc.com/products/Rotary-Encoders_943.html?brand=15461

eg this one
https://www.lcsc.com/product-detail/Rotary-Encoders_CTR-ED231010-FB35A10-A40-1001_C18213495.html
Is a 10 pin, 40 position absolute encoder.  ~ $4.50/1+
Broadly it also seems the more you pay, the more defined and forceful the detent clicks can be.

[Victorman222]

If you need the 18 position switch for the timebase, maybe you could use a typical 10-11 position switch with a range divider switch (as in switch ranges from ms to μs). That is the arrangement that most simple soviet scopes used in order to have a standard and reasonable size switch. Attached is an example of how it looks on the front panel.

[quadtech]

John Broskie's stepped attenuator is a beautiful example of using cascaded rotary switches to get more steps -

https://tubecad.com/2007/04/blog0102.htm