smart implant as voltmeter

[Łukasz997 117]

I need to measure presence of voltage 1.8V DC, minimal current (~10-20 mA). I would like to know not even precise measurement, but if the voltage is present or not (other words - if LED is on or not).
Can I use smart implant to do this? Based on the documentation I hope that I can - implant acting as a 0-10V sensors driver.

I don't want to supply power to the "sensor" (as at the wiring in manual), just take voltage read-out.

 

Can anyone with practical experience advise me what can I pay attention? Especially, how to wire it for two independent "sensors".

In advance - thanks!

Edited January 24, 2025 by Łukasz997

[Martin_N 154]

Look, it's quite academic discussion

From the previous description, it is obvious that one blue was on the GND 24VDC (-) (0V), and the other blue was attached to the cathode of the diode. Internally, GND was connected (at least so Lukasz thought). There would be nothing wrong with this, and it would even be desired (interconnection of both countries of different potentials).

But there is one "academic". We do not know the wiring of the motherboard! Even provided that the pullup is not used and 3 wire wiring is used, we do not know how the diode is connected in the circuit.

In my opinion, the anode can be attached (now I am passing by restriction resistors) by the anode permanently to the positive potential and the cathode to a strengthening transistor that attaches GND. And here, if GND is not permanently connected, but is switched, there may be the problem. Also, the circuit may contain the detection of the diode, there is a disagreement with the capacity, the current collected through the transistor, the impedance changes to the PCB, the removal is disturbed by means of soldered wires (read antennas!), ... just anything.

Without the scheme of the board it is difficult to guess, .. maybe a quality photo will help.

 

To collapse.

If there are two voltage sources (power supply and measured) together via GND (even SI), the voltage reading should work in 0-10V mode in 3-point connection.

 

And do you want another extreme?

We also do not know whether the boiler power supply does not even use symmetrical voltage +24VDC/0VDC and 0VDC/-24VDC.

Or, symmetrical voltage can be except for some low-volt branches.

eM.

Edited January 27, 2025 by Martin_N

[Łukasz997 117]

I did it according Tim__ advice. As I leave the wiring in heater I have to cut one wire only and push the connectors.

A what we have: board does not state an error. When the led is off smart implant reads 5.83 V, when led is on it reads 2 V.

The goal of this experiment is not to measure the voltage, but to unveil the change in circuit. Therefore the goal is achieved - I have the information if the water heating is activated and if the burner is on.

Tim__, it's working as you say, thank you!

 

Thank you, Martin_N for sharing the knowledge. Do you think, that when I leave this as above I can damage the board in a long term? I hope not, but I just want your opinion.

*

According to thread about photo-sensor. I order the light sensor and voltage divider for astonishing amount of 3 euro both (sic!, +delivery :). The sensor incorporates relay, so it can be binary sensor. It seems to me quite valuable to know the result of such experiment to use in other cases. I will assemble this, check and make know in a while.

Please login or register to see this image.

/monthly_2025_01/image.png.0147cf2697cf346218456962601e65db.png" />

[Martin_N 154]

54 minutes ago, Łukasz997 said:

Thank you, Martin_N for sharing the knowledge. Do you think, that when I leave this as above I can damage the board in a long term? I hope not, but I just want your opinion.

 

Hello.

No, using this sensor will not affect or damage the motherboard. All this assuming that there is no short circuit due to the release of the metal case of the photoresistor. You also have to think of a safe location for the board with the converter (relay board). The advantage of this module is probably also the adjustment of the detection level with a trimmer. The disadvantage is the constant consumption when the relay is pulled in. I estimate 50-100mA, if that doesn't bother you...

 

If you would like to "play" further, you can use "only" a phototransistor to connect directly to the binary input SI, for example type: 503PTC2E-1AD

Well... shipping is the biggest expense.

 

Good luck

 

[Łukasz997 117]

I've asked for security of solution with connecting to board and gnd... But I think it is - nothing bad happens.

I achieved my goal, further experiments is only to "enrich the forum". And still, this is safe and universal.

[Łukasz997 117]

To wrap up this topic - I've checked mentioned above module. It turned out that it is absolutely suitable to read even mini-led state of the mainboard which cannot communicate with HC3 other way. The power with smart implant cannot be shared, but it's available voltage divisor 24->5V - if someone dare to put next 1,90 eur (+delivery!) on hazard.
I hope it can be very useful solutions in some cases. And the creators of the smart implant deserve a small monument.