How isolate IO pins of arduino and PSU output ?

Other Hardware General Electronics
1

355139936_963030288146750_3837852927477291040_n
355139936_963030288146750_3837852927477291040_n1152×2048 181 KB

Hello everyone, i will start by saying that i am a beginner of electronics and i don't have much experience hence i am making this post asking for advice from more experienced peopled than me.
Now that i have lowered the expectations :)), let me present my situation;

I have a 12v PSU with 12v 7Ah SLA battery backup that has 2 sets of 13.8v outputs, one of them goes into a board with multiple fuses from where i will be powering my electronics. Presented at the beginning of my drawing, i will call output1 and output2, wich are 2 fused output i am interested of using.

Afterwards i have a simple pir sensor wich gets 12v dc for power, and outputs a signal wich must be interpreted by an arduino mcu board. Nothing fancy so far, i expressed that fact that i will give power for the sensor from output1 and power to arduino from output2. The output of the sensor goes into a digital input pin on arduino.

Now i want to make this setup proof to any external interventions of sabotage as an example would be to apply an overvoltage maybe even 230 ac power to any wires that goes into that sensor and try to fry/affect the arduino input pin/psu wich is also powering the arduino.

For that i have into consideration to use some sort of device that will just intrerupt the wiring in case of not normal operation or even fry itself protecting the other components.

What i need is;
A device wich will protect the sensor output line wich get received by arduino IO pins and not fry them. For that i considered an optocoupler.
Considerations; an optocoupler would work for a digital high/low signal that comes from the sensor, on one side sensor high pin and sensor gnd / on the other side arduino 5v and input pin (with corresponding resistors and wiring but that's not my main subject here).
In case of sabotage for that output line i suppose this will do but what if i want to read analog values instead of digital? this optocoupler is only closing a circuit when it have voltage on the transmitter led side letting the 5v of the arduino flow into the Digital input pin.

For the power side, i have purposely powered the sensor/arduino from 2 different outputs to express that i need some sort of protection on the output1 wich is powering sensors, and in case there will be an attempt of sabotage on the sensor ~12v power wires, the device must interrupt the power and protect the psu itself also the other components powered from the same psu but different outputs and keep them running.

For isolation i considered a 12v dc-dc transformer wich only creates a galvanic isolation between sides but has nothing to do with overvoltage protection.
On same topic i would want to ask if transistors can act as separators in case of overvoltage between collector-emitter and just fry if exeded max voltage rating

I am looking forward for any advise, any help would be appreciated!
Regards, Alex!

2

Have you considered optocouplers?

1 Like
3

Have you read my post ? they would work for digital signals but for analog(varying voltage) i don't know wich one should i pick since i have seen there might be some that depend on the inside led varying brightness received by a phototransistor with variable resistance. For psu side they wouldn't work

4

Nope.

5

For analog isolation consider a Voltage to frequency converter. Opto isolate the frequency and measure that frequency with your arduino.

1 Like
6

sounds good, Voltage to frequency converter or analog to digital converter then pass that signal trough an optocoupler.
What about the psu outputs where i can't use optocouplers and i don't have a separate psu for sensors, if the psu gets affected, whole electronics will suffer

7

This gives you one digital signal = one opto coupler.

You will need some control = more opto couplers.

Look at this Nat Semi app note https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwj_pPLolub_AhX9hf0HHSrbA0UQFnoECAsQAQ&url=https%3A%2F%2Fninova.itu.edu.tr%2Fen%2Fcourses%2Finstitute-of-science-and-technology%2F133%2Fmkm-510e%2Fekkaynaklar%3Fg24521&usg=AOvVaw32lWMSe7QMOM5HlLnYZqoP&opi=89978449

There are isolated Dc/DC converters you can buy 'off the shelf', e.g. Traco for £4 on eBay.

image
image1400×788 56.9 KB

Let us know how it goes :slight_smile:

1 Like
8

For the power side, i have purposely powered the sensor/arduino from 2 different outputs to express that i need some sort of protection on the output1 wich is powering sensors, and in case there will be an attempt of sabotage on the sensor ~12v power wires, the device must interrupt the power and protect the psu itself also the other components powered from the same psu but different outputs and keep them running.
Download Remini Mod Pro

9

The LOC110 is an optoisolaor for analog signals

1 Like
10

i see this module has an Insulation voltage of 1000v dc wich might work for 230 AC, but has a low amperage rating, i will be searching other models. What about when it fails does it intrerupt the circuit or can lead to a short between sides also if it is working like transformer then voltage applied to the output wouldn't induce something on the primary psu side ?
that datasheet is to nice for me to be able to understand something :))

11

This is unclear to me.

I do not know.

I just showed that as an example.

12

i just though, for protecting the psu from overvoltages that might occur, what if i use a 12dc SPD type 1 used for solar pannel systems, wich is supposed to take the overvoltage and conduct it to ground/earth ?

13

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.