# MAX394 IC, use as a switch, query

#### Luca7

Joined Apr 10, 2019
10
I am trying to use an IC called MAX394CPP+, which is a 'Low-Voltage, Quad, SPDT, CMOS Analog Switch'. Attached please find the pin configuration of the IC. The main objective is to use it as a switch.

For testing purposes, I attached a red LED and a 1k ohm resistor both on pins 2 and 4. The problem is both LEDs switch on and I don't know why. Suppose since it is a switch only one LED switches on and not both of them. I tried giving V+ = 5V and V- and Gnd = 0V, I also tried giving V+ = 5V, V- = -5V and Gnd (these where are all written in the datasheet), but none of them worked.

My question is has anyone at least tried to work with this IC pls? Thanks in advance.

#### Attachments

• 40.2 KB Views: 18

#### AlbertHall

Joined Jun 4, 2014
12,157
What was pin 3 (COM1) connected to?

#### Luca7

Joined Apr 10, 2019
10
I connected it to a 5V coming from an Arduino

#### MisterBill2

Joined Jan 23, 2018
13,139
With no information about what was connected to the input, pin #3 ( submitted this before I looked at the post that arrived while I was entering my post) , nor what the power supply was, nor what was connected to the other pins, there is no way any useful analysis can be given. Nor will I even try.
And note that for a CMOS devices every input must be connected to an appropriate level.

Last edited:

#### crutschow

Joined Mar 14, 2008
30,801
What is the other end of the series LED-resistor pair connected to?
What is pin 1 connected to?

#### eetech00

Joined Jun 8, 2013
3,418
The switch should be connected this way if used with a single supply:

The switch will close the NO contact when the control input is high.
For your application, the control switch (SW) would be replaced by an arduino digital output.

Last edited:

#### Luca7

Joined Apr 10, 2019
10
With no information about what was connected to the input, pin #3 ( submitted this before I looked at the post that arrived while I was entering my post) , nor what the power supply was, nor what was connected to the other pins, there is no way any useful analysis can be given. Nor will I even try.
And note that for a CMOS devices every input must be connected to an appropriate level.
You are right and I have to apologise. Attached please find the circuit used.

#### Attachments

• 38.3 KB Views: 14

#### Luca7

Joined Apr 10, 2019
10
What is the other end of the series LED-resistor pair connected to?
What is pin 1 connected to?
This is my circuit, at least what I tried to do. Thanks

#### Attachments

• 38.3 KB Views: 8

#### Luca7

Joined Apr 10, 2019
10
The switch should be connected this way if used with a single supply:

View attachment 263214

The switch will close the NO contact when the control input is high.
For your application, the control switch (SW) would be replaced by an arduino digital output.
Wow! You are really helpful. Much appreciated. I will try it, and keep you updated on what will happen.

#### AlbertHall

Joined Jun 4, 2014
12,157
The ground of the power supply must be connected to the ground of the arduino.

#### Luca7

Joined Apr 10, 2019
10
The ground of the power supply must be connected to the ground of the arduino.
I thought that if I do that, there will be a conflict between the grounds. I will try that. Thanks

#### MisterBill2

Joined Jan 23, 2018
13,139
OK, I see four things wrong: There are 3 unaddressed inputs and the control voltage to the input is not right. It should be either zero or 5. Having the input at a limit is asking for the sort of problem that you are having. 2.4 is defined as a limit, not a target. use 5 vots and zero volts and it will work as specified.

#### eetech00

Joined Jun 8, 2013
3,418
Wow! You are really helpful. Much appreciated. I will try it, and keep you updated on what will happen.
I'm curious.
After reviewing your circuits, why not just drive the LEDs directly with one or two arduino digital output(s)?

#### MisterBill2

Joined Jan 23, 2018
13,139
What was pin 3 (COM1) connected to?
I'm curious.
After reviewing your circuits, why not just drive the LEDs directly with one or two arduino digital output(s)?
Given the pricing shown in that reference in the early post, $16.54 each, I would choose a different driver. A CD4049 with al six sections in parallel, puling low and running on 9 volts should be good for 30 mA, and that IC uses a much cheaper socket, and costs under$1 from a reasonable supplier. At east they did a couple of years ago. No need for a precision switch to turn on an LED.

#### eetech00

Joined Jun 8, 2013
3,418
Given the pricing shown in that reference in the early post, $16.54 each, I would choose a different driver. A CD4049 with al six sections in parallel, puling low and running on 9 volts should be good for 30 mA, and that IC uses a much cheaper socket, and costs under$1 from a reasonable supplier. At east they did a couple of years ago. No need for a precision switch to turn on an LED.
I suggest driving the led directly with digital output. The TS LED circuit is only drawing roughly 6-7 mA each anyway. The arduino output can drive 30-40mA.

#### MisterBill2

Joined Jan 23, 2018
13,139
No argument with that. The benefit of a buffer IC is if something "goes wrong", then a cheap and easy to replace part suffers instead. A buffer is cheap insurance.

#### eetech00

Joined Jun 8, 2013
3,418
No argument with that. The benefit of a buffer IC is if something "goes wrong", then a cheap and easy to replace part suffers instead. A buffer is cheap insurance.
I see your point, but the risk is extremely low, and an Arduino, while much more than a \$0.50 part, are still pretty inexpensive.

#### djsfantasi

Joined Apr 11, 2010
8,574
I suggest driving the led directly with digital output. The TS LED circuit is only drawing roughly 6-7 mA each anyway. The arduino output can drive 30-40mA.
I agree.

Depending on what else the Arduino is doing.

While the specs say that an Arduino can drive 30-40 ma, that’s the maximum rated value. Designing for a 20 ma output is safer.

Plus, if the Arduino is doing anything else (driving a speaker, servo, using an SD card, etc…), then one has to account for the 200 ma total current that an Arduino is limited for.

#### Luca7

Joined Apr 10, 2019
10
Well, I am blown away by all of your responses and by your kindness. This is the first time I am asking on an electronics forum and tbf it's a pity I never asked before. Perhaps I was too scared or shy asking a question on here... anyway.

This is a project, where I am trying to replicate the joystick of an electronic wheelchair using a wireless remote control (don't worry I am not doing the testing on a wheelchair of a person using it. We have an electronic wheelchair at home and we stopped using it, so I am using its joystick and power module). So first, I found the voltages that the lever is outputting, and it's from 1.1V to 3.8V on each axis. So I replicated these voltages and the joystick by using an Arduino and a PS3 controller, respectively. Everything worked how I planned it to. Now I only needed a sort of switch, such that I can move the electronic wheelchair from the PS3 controller or from the joystick,

I thought a possible solution would be the MAX394 but I did not manage, and I asked here for help. To be honest with you I managed with this component bought from Mouser UA2-5NJ and it worked. I only needed an analogue switch such that the PCB found in the wheelchair will accept the voltage s from the joystick or from the Arduino.

I will still try to work with the MAX394 since it's not a cheap component and it would be a pity if I do not manage to work with it.

#### Luca7

Joined Apr 10, 2019
10
The switch should be connected this way if used with a single supply:

View attachment 263214

The switch will close the NO contact when the control input is high.
For your application, the control switch (SW) would be replaced by an arduino digital output.
Thanks a lot. The IC worked!