OTmonitor prints out thermostat disconnected and connected

This Forum is about the Opentherm gateway (OTG) from Schelte

Moderator: hvxl

OTmonitor prints out thermostat disconnected and connected

Postby malek » Fri Jan 13, 2017 11:10 pm

I'am working for a school project to make a opentherm gateway. I have solder the opentherm gateway and i have tested the gateway.
I have connected the opentherm gateway with the boiler and the thermostat(Honeywell Round Modulation). I get the data from the boiler but the thermostat is disconnected and the otmonitor prints out that constantly disconnected and connected.

See the picture of the otmonitor.drive.google.com/file/d/0B3Mgf9SlnCcoNX ... sp=sharing.

What can be the problem and how can i solve it?

Thanks in advance!

Kind regards,

Malek Sediqi
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Sat Jan 14, 2017 12:32 am

The gateway will report "Thermostat disconnected" when the voltage on AN0 (pin 17) goes above 2.38V, which translates to more than 19V on the Opentherm line. The Opentherm spec specifies a maximum voltage of 18V for normal signal levels. Normally you would only get that when there is nothing connected on the thermostat connector. So check that the wires between the gateway and the thermostat are properly connected with the screw terminals on both ends.

If R5 or R6 has the wrong value the voltage on AN0 can also go too high. So check that these resistors have the proper values, although they look OK in the picture you attached to your previous topic. Finally, if the resistors both happen to deviate from their nominal values in the worst possible combination (R5 too low and R6 too high), you may get a false positive with normal Opentherm signals. To fix that, you can put some high value resistor (100k or so) in parallel with R6 to lower its value a bit.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Sat Jan 14, 2017 11:35 am

Thank you for the reply,

I have checkt the wires between the gateway and thermostat and i have changed the wires and it didn't help.

I have checkt the R5 and R6 and the R5 has 30K ohm and R6 is 4.6k ohm.

I did again the test of the OTGW website and one thing was wrong and
that is this test :

Measure the voltage on pin 18 of the IC1 socket with pin 3 left open and again when it is connected to ground.

the first test with pin 18 was 0V. But the second test if the pin 3 is connected to the ground then the pin 18 gives 2.85V. Can that be the problem and how can i solve it.

After i am done with the project i will post the link of the project.

Thanks in advance!

Kind regards,

Malek Sediqi
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Sat Jan 14, 2017 11:48 am

Pin 18 is used by the boiler interface. That part appears to be working OK. So there's no need to mess with that side.

30k for R5 is a bit low. In combination with an R6 of 4.6k, that would put the level for detecting a disconnected thermostat at 17.9V. But that is still a perfectly acceptable Opentherm signal level. So as I suggested, also lower the value of R6 a bit by putting 100k or thereabouts in parallel.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Sat Jan 14, 2017 2:23 pm

I have added the 100k parrallel to R6drive.google.com/file/d/0B3Mgf9SlnCcoc3 ... sp=sharing. The gateway didn't print out the disconnect and connect but it still doesn't connect with the thermostat. I have changed the preference voltage and it still doesn't recognized the thermostat. The voltage of pin 17 is 0V if the thermostat is connect. Is the way i have added the 100k to R6 good or is there something else not working in my opentherm gateway.

I have made a print screen of the OTmonitor it prints out something that i don't recognize.
drive.google.com/file/d/0B3Mgf9SlnCcoWH ... sp=sharing
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Sat Jan 14, 2017 11:29 pm

Oke pin 17 was 0V because the 100K was wrong placed. I have checked again pin 17 and it is still 3.89V,the R5 is still 32K and the R6 paralle with 100K is dropped to 4.4K ohm.
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Sun Jan 15, 2017 8:00 pm

Pin 17 gives still 3V with thermostat connect to the gateway, is there away to solve it, because it doesn't detect my thermostat.

Kind regards,

Malek Sediqi
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Sun Jan 15, 2017 10:24 pm

Your information is a bit confusing. You report that pin 17 is still 3.89V when you have never before mentioned the voltage and now it is "still 3V". You also say that R5 is still 32K after saying earlier that it is 30K. It's difficult to help if you keep throwing up different values without any indication of what happened to cause the changes.

With the latest resistor values you report, the voltage on pin 17 can only be 3V if the voltage on X1 is 25V. It shouldn't be that high with a thermostat connected.

I suggest you check the voltage on X1 and pin 17 in 3 situations:
  • No thermostat connected: Expected values 25V and 3V.
  • Thermostat connected: Expected values 6V and 0.75V.
  • X1 shorted: Expected values: 0V and 0V.
You may also want to run test #5 of the diagnostic firmware.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Mon Jan 16, 2017 9:22 am

Ow, sorry for that,
i was forgotten to tell that i have added a 14K resistor parallel to R6 to let pin 17 of IC1 drop down to 3V. Without the 14k resistor pin 17 is 3.89V. The R5 is 32K, i didn't write it right, sorry for that.
I will do the checks that you recommended me, i let you no what the results are.

Kind regards,

Malek Sediqi
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Mon Jan 16, 2017 5:18 pm

There must be a short somewhere. If you still have 3V with a 14k resistor parallel to R6, it means there is almost 1mA going through that combination of resistors. If the circuit is as it should be (and R5 is 32k), you would need to have more than 31V on X1 to achieve that. The power supply doesn't provide that much.

If I understood everything correctly now, R5 is 32k and R6 is 4.6k. Those values should be OK. That will result (if everything works correctly) in only detecting a disconnected thermostat if X1 goes above 18.96V. So get rid of the additional resistors and figure out where the additional voltage comes from. If the checks I suggested earlier don't provide a clue, try to remove IC1 and then check the voltages on X1 and pin 17 of the IC1 socket both without and with the thermostat connected. Those should normally be pretty much the same as with IC1 in place. If they are not, it's an indication that the additional voltage is coming from IC1.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Mon Jan 16, 2017 7:38 pm

Oke i have done the test, this are the results from the first test, i have removed adittional resistors and i use a new Multimeter because the other wasn't working well.

I suggest you check the voltage on X1 and pin 17 in 3 situations:
No thermostat connected: Expected values 25V and 3V.
Result:
PIN 17 = 3.9V
X1 = 31V

Thermostat connected: Expected values 6V and 0.75V.
Result:
PIN 17 = 0.100V
X1 = 0.800V

X1 shorted: Expected values: 0V and 0V.
X1 = 0V
PIN 17 = 0V

This are the results from the second test :

Without PIC
With thermostaat :
• X1 : 31V
• Pin 17 : 3.9V
Without thermostaat :
• X1 : 31V
• Pin 17 :3.9V

With PIC
With thermostaat :
• X1 : 0.800V
• Pin 17 :0.100V
Without thermostaat :
• X1 : 3.9V
• Pin 17 : 31V

Does this mean that my pic is broken?
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Mon Jan 16, 2017 9:24 pm

Woah, you really have 31V on X1 when nothing is connected? Then you probably used a different transformer than suggested. With the listed 15V transformer you should only get around 24V. But as long as the 7805 can handle it, that isn't actually a problem.

All your measurements look like the gateway is behaving correctly, but you have an on/off thermostat connected instead of the Honeywell Round Modulation you said. That's why you get almost nothing (< 1V) one time and the full 31V another time; typical on/off thermostat behaviour.

It is actually allowed for an Opentherm thermostat to pull the line that low. Most don't because they need some voltage to run on. But to be sure, I double-checked with my own Honeywell Round Modulation. I can confirm that it only pulls the line down to 6.1V.

So, check your thermostat. It doesn't appear to be an Opentherm thermostat. If you still believe it is, you can double-check with test #5 of the diagnostics firmware.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Tue Jan 17, 2017 10:44 am

Thank you for your hulp, I'm going to try it with a other thermostat(Letting my parents buy a new one :D :D ).
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017

Re: OTmonitor prints out thermostat disconnected and connected

Postby hvxl » Tue Jan 17, 2017 5:38 pm

Does that mean you confirmed that your thermostat is indeed an on/off type? A round modulation model does actually say "MODULATION" on the front. There should also be sticker with a type number inside. T87M#### models work with Opentherm. T87G#### are on/off.
Schelte
hvxl
Senior Member
Senior Member
 
Posts: 1012
Joined: June 2010

Re: OTmonitor prints out thermostat disconnected and connected

Postby malek » Wed Jan 18, 2017 10:50 am

Yes it was a on/off thermostat. I have changed it with a Honeywell round modulation now.
I thought first that my thermostat was a honeywell round modulation because we had changed four years ago the boiler and the thermostat, that is why i was pretty sure that i had a opentherm thermostat. Everything works fine now, thank you for your hulp.
malek
Starting Member
Starting Member
 
Posts: 12
Joined: January 2017


Return to Opentherm Gateway Forum

Who is online

Users browsing this forum: No registered users and 3 guests