(This might be a long read for a simple question but I suspect there are solutions to my problem that I'm not aware of so I'll try to describe what I want to do and see what you all suggest)
My sister in-law has an old vintage radio cabinet with a speaker (electronics were gutted a long time ago). I am planning to bring it back by installing a small amplifier with a bluetooth module so it can be used as a kitchen type speaker for music/radio/podcasts (no audiophile grade setup ;))
It has the original knobs and I will use one for volume and one for power. My plan was to simply switch the hot lead from the power supply to the amplifier with a rotary switch - and here is my problem. How to safely use a rotary switch as a power switch regarding power rating. The rotary switches I have on hand is an alpha 2P6T (this one) (https://www.banzaimusic.com/Alpha-2P6T-Rotary-Switch.html) but I have a hard time finding the right datasheet. I've looked on Mouser (https://eu.mouser.com/c/ds/electromechanical/switches/rotary-switches/?m=Alpha%20%28Taiwan%29) - is the first from the left on the 3rd row the right one?
I also have a 1P12T that looks like an "alpha" switch but is labeled "EAGLE". (Searching for that only yields results about the eagle software and library questions though.) Probably bought this one from Tayda or maybe musikding.de.
The modules I have been looking at are these ones:
XH-A158 (built in bluetooth) with a DC in of 5V https://www.amazon.com/XH-A158-PAM8403-Bluetooth-Amplifier-Wireless/dp/B0C5QTFCT4 (https://www.amazon.com/XH-A158-PAM8403-Bluetooth-Amplifier-Wireless/dp/B0C5QTFCT4)
And this one:
Velleman 2x5W that needs 6-14Vdc / 1A (as well as a separate bluetooth module that also needs power) http://www.velleman.co.uk/contents/en-uk/p115.html (http://www.velleman.co.uk/contents/en-uk/p115.html)
For power supply I was thinking I would use one from the drawer of scavenged items (say a 5-12V 1A or something). And I assume whatever switch I need should be able to handle the power supply max (and not the maximum draw of the circuits).
And finally to my questions:
How do I do this? - am I overthinking this?
Can anyone help me find the datasheet for the alpha pot?
Should I use the rotary switch to control a relay instead?
You shouldn't be using those rotary switches for mains. That are not safety approved to be connected to mains. Even if you see switches rated with 125VAC and 250VAC it doesn't mean they are safety approved for connection to mains. (If you use a relay and these switches connect to mains voltages it's still not safe.)
Stuff like this is a lot harder to find these days than the old days.
This example looks like it could be IEC rated which is OK for Europe and UK. For US you need UL and it's not 100% clear they cover UL (there is a UL version of the same IEC standard).
https://www.hificollective.co.uk/switches/lorlin-4a-dpst-rotary-mains-switch.html
The datasheet doesn't say much. I haven't read that standard to see what loopholes there are.
Thank you for your reply!
My intention is not to switch the full mains (the 220V, 10A) but to switch the power from the power supply (the same way the tiny slider switch on the velleman kit works). But maybe the same problem persists?
Quote from: Keeb on April 14, 2025, 12:34:50 AMMy intention is not to switch the full mains (the 220V, 10A) but to switch the power from the power supply (the same way the tiny slider switch on the velleman kit works). But maybe the same problem persists
Got it. Sorry I missed some details this morning.
Well the current rating of the Alpha switches is low, like 300mA. The Lorlin CK types will do 1A. They are the Black and/or White plastic looking rotary switches. Not sure what the current ratings of the knock-off brands are though. Given they have multiple contacts it wouldn't hurt to wire the contacts in parallel.
I think I will buy a Lorlin. Either this RMS1130F (https://www.ebay.com/itm/365399474177?_skw=Lorlin+rms1035&itmmeta=01JRSDD97ZTKFTF0NZH0VJ3ZHF&hash=item5513818001:g:DhgAAOSwLtFnr5Si&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1et0cC7tiHq%2B5aL5vSKoktJ4O2vppUJPEGsWvV1F2oahtz1TU1Pd%2FMt5zfwjo1dP29YrGuGuueaX2jQMjspoVbaOIn2i9NciMILVwLlYFHFqj%2BHx%2Ffdm3Ix3SxBbtZIcz0ZjVtUFs4bpKAT9XISXGNIvF1TZW%2B6KkzogUVXJ%2B5zXOtBMGRXzvXSfPhnKN%2BT63DN5%2BDFLNQsFyau%2Bek78966YN5%2FUK6DotUkFHcbVBeCu9xwTrGEkRA5d%2BJrPYMCPcs%3D%7Ctkp%3ABk9SR-CUta3GZQ) or this RMS1035 (https://www.ebay.com/itm/204755445592?_skw=Lorlin+rms1035&epid=2254314697&itmmeta=01JRSDD97Z1DV1597F895R7D7J&hash=item2fac602758:g:QzkAAOSwUdNmJMTZ&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1cz4NF9cXvQhovZOjGjUF5NH88v11cI0hSi%2FVr%2FJtuMgv9C8JhAoCAUVuBnsl7Zz1PO0XapqT7waK2oQ8u8k7sL7UGdSz7CZxAlOY4EIAtbu4%2FoMtgMCkOSJE8dz1whhN%2BZG%2BvXAhzw2KzB1%2FAspGzK65Wrrf2vq5IC1bqq%2FyZS%2FBoAh8q8S1RICdYNvzsTbmAyqIS74TZQLPIdcvwD8CFCYaIEkxFxlGrVhzNGSMS6RXp%2BF07DQrr88WDakGqeXXA%3D%7Ctkp%3ABk9SR-CUta3GZQ)
I fail to see the difference even though they have different part numbers (one has cheaper shipping though).
If it's worth doing it's worth overdoing, right?
https://datasheet.octopart.com/RMS1130-Lorlin-datasheet-8501713.pdf
terminal type - standard metric switches
SOLDER - RMS1035
PCB - RMS1130
F - no spindle flat
You can still buy long-shaft pots with a switch on the back, just like most vintage radios used for power...
How about switching power via a transistor/mosfet instead?
Quote from: duck_arse on April 14, 2025, 11:14:02 AMhttps://datasheet.octopart.com/RMS1130-Lorlin-datasheet-8501713.pdf
terminal type - standard metric switches
SOLDER - RMS1035
PCB - RMS1130
F - no spindle flat
Thank you!
Quote from: merlinb on April 14, 2025, 12:18:45 PMYou can still buy long-shaft pots with a switch on the back, just like most vintage radios used for power...
I would love that but the radio has two holes in the front...
Quote from: Keeb on April 14, 2025, 02:57:35 PMbut the radio has two holes
Put a whole switch-pot in the hole but only use the switch. Probably come out cheaper than a naked switch, and will take a normal knob. Ignore the pot part. Or let it control a green LED's brightness.
Quote from: duck_arse on April 14, 2025, 11:14:02 AMhttps://datasheet.octopart.com/RMS1130-Lorlin-datasheet-8501713.pdf
terminal type - standard metric switches
SOLDER - RMS1035
PCB - RMS1130
F - no spindle flat
Those non-changeover types would be best.
QuoteI would love that but the radio has two holes in the front...
Use the second hole for a tone control (active or passive). Or use a concentric pot for bass and treble. Or add a preamp (gain) control. Or use the hole to add a headphone out. Or an auxiliary in for a CD player or similar. Or a guitar input (I did that to an old table top radio that I have).
You may have figured out that I like to make things as complicated as possible :icon_twisted: .
Yep, lots of things you can do with a second hole! A tone control, a cool-looking lamp, an aux input... Tone control would be good because that's what vintage radios always had, so it keeps the look-and-feel of the original!
You guys have convinced me to use a switched pot and a tone control :icon_biggrin: . I've breadboarded a simple RC lowpass filter with a pot for resistor and it sounds good.
I'm ordering this pot (https://www.mouser.se/ProductDetail/652-PTR902-2020FA503) from Mouser (it handles 3A at 16V and I'm using a 9V/1,3A supply).
The only problem I have is that the stock pot, log 50K, is quite steep. The usable range is small before it gets too loud. I guess it has to do with the speakers I'm using? I tried lowering the volume pot all the way down to 1K but it's the same. Before I order the pot from mouser, I would like to hear if you guys have any suggestions how to make the volume pot less steep/have more usable range?
I went with the Velleman kit by the way. I traced the amplifier schematic and it's basically the same one from the TDA1517 datasheet (https://www.nxp.com/docs/en/data-sheet/TDA1517.pdf), page 8. Some cap changes and a stereo pot before the input as a volume control.
Thank you all for all the help!
Sounds like you need to add a series resistor between the signal input and the pot, to knock down the level before it reaches the pot. You might have cut a PCB track to install it between the jack and pot.