ph-4502C temperature pin problem

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I have the following hardware

  1. Raspberry pi 3 B+
  2. 8 Channel relay
  3. DHT11 temperature and humidity sensor
  4. PH-4502C DIY MORE analog PH meter
  5. MCP3008 ATD
  6. Keyestudio TDS Meter V1.0

So far I got everything working using nodejs, I am building an automated hydroponics system and the last part I received was this analog PH probe and module, I have not gotten to the coding part (of the PH, everything else is already fully working) as I have not been able to get all pins connected, note that the module is for arduino.

I have connected all the pins to the corresponding areas on the pi board and the ATD module, all works fine except that whenever I connect the temperature pin the pi won’t boot so I am obviously connecting something wrong.

While searching on the internet I could not find other people that have done it as it seems that everyone has issues with that pin, I am attaching an image I created of the current setup.

My question is, has anyone been able to get this module working when using that pin? if so can you provide me with details of how it was connected?

current hydroponics setup

enter image description here

Pins description:

  1. V+ : Power 5v
  2. G : Power ground
  3. G : Signal ground
  4. Po : pH output (analog)
  5. Do : Level signal output (digital)
  6. To : Temperature output (analog? maybe not and that could be the reason is not booting up)

Unfortunately the module information is in Chinese so it is kind of hard to figure this one out.

The module has two leds, when I connect the temperature output pin both leds are red and the pi won’t boot, when I remove the temperature output pin only one led is red and the pi boots.

enter image description here


@joan with your mention of the power required for the relay I tested if the issue was insufficient power, I removed everything except for the PH module but the same thing happened. I am also attaching real images of the module when all pins are connected and when the temperature pin is not connected.

Pin not connected: Pin not connected

Pin connected: Pin connected

  • What is the temperature pin? Let’s have a clear photo of the connections to the component which cause the failure. Frankly I doubt if the relay could be fully operated from the Pi power supply. – joan Jan 15 at 16:35
  • The temperature pin is the pink one that goes to MCP3008 CH2. The relay is fully operational, it controls the pump and the lights without any issues for months. – Tlacaelel Ramon Luis Jan 15 at 16:40
  • Are you sure your MCP3008 inputs Ch0 and Ch1 are in single ended mode? The comments/chats of the following might help: (1) raspberrypi.stackexchange.com/questions/106761/… (2) raspberrypi.stackexchange.com/questions/106728/… – tlfong01 Jan 16 at 2:37    
  • I mean if your Ch0, Ch1 are in differential mode, and let us say now Ch0 is 1V, Ch1 is 3V, then the input voltage is a negative -2V, which MCP3008 is not loving it, and in this case, there is no guarantee that no nothing won’t meltdown or blow up, Rpi might now R.I.P and never boots up again 🙂 – tlfong01 Jan 16 at 3:21    
  • @tlfong01 Ch0 is connected to a device that is working, Ch1 is connected to a pin in the PH module which is working, the only issue I have at the moment is the temperature pin which is connected to CH2 – Tlacaelel Ramon Luis Jan 20 at 17:17
  • Ok. Congratualtions, so you have solved the pH meter’s wierd temperature pin problem. I would suggest you to post an answer, telling all other pH newies weeping in the dark, how you solved the problem, how to use the temperature pin etc. – tlfong01 Jan 21 at 1:50   
  • Your question is on MCP3008 Ch0 and Ch1, connected to the pH meter. Now your new question is on Ch2, connected to DH11. I would suggest you to ask a new question. I am happy to follow up with your new questions. Cheers. – tlfong01 Jan 21 at 1:53   
  • @tlfong01 I am unsure what the problem is and you don’t need to be mean, if you don’t want to help it is fine but if you do you could at least read the question properly, I have not solved my problem, the problem is on the temperature pin of the PH sensor which if you had looked at the connections you could have seen is connected to CH2 and DH11 si not even connected to MCP3008 – Tlacaelel Ramon Luis Jan 27 at 18:25
  • @Tlacaelel Ramon Luis, I am sorry that I might have misled you that I am a mean guy. Let me see what might have caused the confusion. So I read your question a second time. I read the following at the end of your question. “My question is, has anyone been able to get this module working when using that pin? if so can you provide me with details of how it was connected?”. My apologies that I might have wrongly assumed that it was your only question. / … – tlfong01 Jan 28 at 1:12   
  • I overlooked hat your second question is on DHT11. I thought I have answered your question by referring to my old answer, that it was the NTC’s temperature, … / to continue, … – tlfong01 Jan 28 at 1:12   
  • @tlfong01 this question is NOT about DHT11 but to what the title says “PH meter PH-4502C” the PH meter has a temperature pin which is in no way related to the DHT11 temp/humidity sensor which as I have stated, is fully working, in fact everything is working except for the temperature pin in the PH sensor. The temperature pin in the PH sensor is for the temperature compensation and not the ambient temperature as the DHT11 provides. The reason I mentioned all the hardware is because maybe someone already went through this and something in the hardware was the culprit. – Tlacaelel Ramon Luis 2 hours ago
  • OK. I think there is some misunderstanding between us. But let us not try to find out the cause of misunderstand for now, and focus on the question. Let me make the question as simple as possible but not simpler. I think of a couple of versions: (1) How to use MCP3008 to read an analog signal, (2) How to use MCP3008 to read a NTC thermister? (3) How to read the the temperature pin in the ph4502C ph meter? Comments and counter suggestions welcome. Cheers. – tlfong01 24 mins ago   
  • I read your question a third time: “[My] question is, has anyone been able to get this module working when using that pin? if so can you provide me with details of how it was connected?”. Now another rephrasing of your question. (4) How to connect that pin (differential mode necessary, or singled ended OK?) Can I get the module working without using the temperature pin? If yes, (a) why? and (b) is there is any better way to replace the temperature pin, and (c) also is there a better ADC than MCP3008? – tlfong01 11 mins ago    

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