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Forum Index : Microcontroller and PC projects : MAX335 8 Channel Analog Switch

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asknik2022
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Joined: 26/03/2022
Location: United Kingdom
Posts: 68
Posted: 10:05am 21 May 2024
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I have been using a Maxim MAX335 8 Channel Analog Switch which is controlled by SPI
I have been searching for a 4 channnel version and wondered if any one on this forum could help.
 
oh3gdo
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Joined: 18/11/2021
Location: Finland
Posts: 43
Posted: 11:09am 21 May 2024
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https://www.tme.eu/gb/katalog/?params=383:1443902_number-of-channels:4&onlyInStock=1&queryPhrase=analog%20multiplexer
Here is 4 channel analog multiplexers
Pekka
 
Volhout
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Posted: 11:09am 21 May 2024
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ADGS1212 or ADGS1412 = 4 STSP
ADGS1209 or ADGS1409 = 2x 4:1 mux

Volhout
Edited 2024-05-21 21:16 by Volhout
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asknik2022
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Posted: 02:02pm 21 May 2024
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I was hoping that there was a Through hole version.

An alternative, can someone suuggest an alternative way to do the folowing without using transistors.

I am using the MAX335 in conjuntion with an ULN2803A to independantly control 4 12V relays in order to switch between various Audio inputs (eg, Phono,Tape,cd etc) via the SPI interface on a Pico
I don't want to waste 4 pico pins as I am also controlling LCD and PGA2310 Audio chip via SPI and want to keep as many pins availbale for future expansion etc.
 
Andy-g0poy
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Joined: 07/03/2023
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Posted: 02:45pm 21 May 2024
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Add a spi based io expander and use that to address the switch. You can then consider things such as the CD4051/2/3 and the 74HC4051/2/3

Andy
 
Mixtel90

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Joined: 05/10/2019
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Posted: 03:56pm 21 May 2024
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Personally I'm old fashioned and would attempt to remove all computer noise from anywhere near audio signals, even if that means using four IO pins, four transistors and four gold flashed contact relays. Layout is everything, keep audio leads short and run long, clean DC signals to the relay coils rather than SPI to a chip. It takes up more PCB but IMHO that's minor inconvenience.

If one signal is the default the relays can be a tree (one spdt, one dpdt), so you only need two pins to select 00. 01, 10 or 11. It's a good idea to think about output muting during any input switching too, no matter how you do it.
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
asknik2022
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Joined: 26/03/2022
Location: United Kingdom
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Posted: 04:23pm 21 May 2024
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Audio Relay board.pdf


This is the circuit diagram of my relay board using the MAX335 and it works very well and I dont hear any computer noise at all.

However since I am really only using 4 channels and it is getting harder to find (at a reasonable cost) the MAX335 chips in Through Hole that I am looking for an alternative

The inputs 5 and 6 are also programmable via the MAX335 as an input or output mode (eg record out)
 
Mixtel90

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Posted: 07:40pm 21 May 2024
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It's getting more difficult to get through-hole anything now, especially ICs.  :(
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
Volhout
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Posted: 10:11pm 21 May 2024
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Andy,

Typically you can connect a 74HC595 to a SPI bus (even in combination with other SPI peripherals) and use the 8 outputs to drive the ULN2803.
And these are in DIL-16.





OE  =     low
SER =     SPI data in
SER_CLK = SPI clock
SRCLR =   high
RCLK =    latch pulse low-high-low to transfer data to output pins


Volhout
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phil99

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Joined: 11/02/2018
Location: Australia
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Posted: 10:53pm 21 May 2024
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The 74HC595 can be driven with just 1 Pico pin by using Bitstream to combine the signals. A handful of other components separate the various signals for the 74HC595.
74HC595 with 1 pin control
The post has a few edits with the final circuit toward the end.
The last TBS upgrade has mangled some of the example code. If anyone is interested I can re-post it.
 
Volhout
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Posted: 07:30am 22 May 2024
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Hi Phil,

I missed this when you published it. Nice...
But there is already a SPI bus on the board. So using a 595 as SPI device look simple (you can even use the chip select (active low) to latch the data, since the RCLK (latch) line is edge sensitive...

So wire it like the MAX335, and send only 8 bits...

Volhout
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asknik2022
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Joined: 26/03/2022
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Posts: 68
Posted: 07:51am 22 May 2024
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Thank You Volhout

This is very interesting and I will experiment etc.
 
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