Thanks
I have connected 3 and 4, removed the bridge and unplugged c and t. Then connected 1 & 2 directly to c and t. This does not seem to activate the refrigeration unit. Did I miss something? I have power to the new unit and set it to 2 degrees, ambient temp is reading 24.5.

 

Oops... had the unit set on heat... works fine now. Thanks so much....

 

Thanks
I have connected 3 and 4, removed the bridge and unplugged c and t. Then connected 1 & 2 directly to c and t. This does not seem to activate the refrigeration unit. Did I miss something? I have power to the new unit and set it to 2 degrees, ambient temp is reading 24.5.

Remember C to T is a loop with a set resistance ( in debes' case this resistance can be changed) with a set compressor speed. So it is important that the resistor is part of this circuit, otherwise the pump will run at its slowest speed.

 

Thanks Daryl.....I reckon the chiller box will be getting a serious workout in those SA temperatures..

As far your comment re a circuit which was temperature/ speed related would be ideal...I totally agree. However I am still curious on how Merlin actuates the speed change using a formula based on run time duration etc. The search goes on.
All the best for 2016......Cheers, Bjorn

 

My thaughts on this are that the beter way is speed controlled by the temperature as in the Waeco system. Where if the temperature rises too high the processor then gives a higher compressor speed. then reduces it when the temperature is nearer where it should be. That being said im not into processor design. My approach in portable 12V DC refrigeration is simple is best. I do have 2 Waeco fridges, but I also converted a Evakool fiberglass esky which has far beter insulation than the Waecos. I just used a $15 electronic thermostat from Ebay. My compressor speed has a switch for economy 2000rpm & power 3000rpm. It spends most of its time on the economy seting, The power setting is only used if ive loaded the fridge up & want it cooled quickly, then it lives on economy. This is my converted Esky.View attachment 97515 View attachment 97516 View attachment 97517 View attachment 97518

what is circuit board next to diagram for ?? is it easy to do this switch on my danfoss db50f ??

 

Has anyone been able to redesign the power stage for the Danfoss BD35F. I have one that has blown FETS on the power stage. I have extended them to a separate heatsink, and unit runs on 24V, but not on 12V. the inverter is working, generating the 35V, and compressor kicks with a high frequency buzz, then gives compressor start fail indication. I have written code to simulate 3 phase using a PIC microcontroller, and applied it to a FET power stage, but was unsuccessful. Has anyone tried to do this and to what degree of success?

 

I would have thaught it would be easier to replace the MOSFETs on the board. If it runs on 24V & not on 12V, I would be suspicious that your wiring to the switching assembly is too long & not thick enough to carry the current. Interested as to how you get on with this project.

 

I would have thaught it would be easier to replace the MOSFETs on the board. If it runs on 24V & not on 12V, I would be suspicious that your wiring to the switching assembly is too long & not thick enough to carry the current. Interested as to how you get on with this project.View attachment 120875 View attachment 120876 View attachment 120877 View attachment 120878

I wanted to replace the FETS on the board, but couldn't get enough heat in the FETS to release them from the board. Any suggestions on how to do this? I am also convinced that the issue that you mention (leads etc)is the problem in this case, as I saw different responses once I put thicker wires in place. As far as my PIC project went, I would switch on one FET on the positive rail, and switch on the two other on the negative rail, and rotate this signal, but I get different waveforms on the Danfoss controller, so I am also doing something wrong here. I think it would be easier to get the Danfoss unit working, but in the long run, this is what I'd like to do. Thank you so much for your response, there is precious little info on this subject.

 

To remove the FETs I first used Solder wick on the small legs, then re heated them with a soldering iron & bent each one up. Next I used a large soldering iron with a chisel tip that would fit betwean the FETs & removed them. Was not that hard to do.

 

To remove the FETs I first used Solder wick on the small legs, then re heated them with a soldering iron & bent each one up. Next I used a large soldering iron with a chisel tip that would fit betwean the FETs & removed them. Was not that hard to do.

Thanks I'll give that a try, I just cut off all the other legs....I just didn't want to damage the board underneath. I am sure that the controller will work after that.

I won't put the PIC controller to bed just yet.....Thanks

 

Thanks
I have connected 3 and 4, removed the bridge and unplugged c and t. Then connected 1 & 2 directly to c and t. This does not seem to activate the refrigeration unit. Did I miss something? I have power to the new unit and set it to 2 degrees, ambient temp is reading 24.5.

Hi.
I just spent my time off asking with dads camper.
My mate thinks I'm crazy. I could be right, it works (he's engineer). I've got a powered thermostat for 12v fridge. Compressor is danfoss 101n0220 or there about.
It was piggybacked backed everywhere.
I've got an extra cable spliced into main +, there is. Pos+ and neg+ leading towards internal and light/near original mechanical thermostat. I rewired that in. I plugged my fan in (missing a pos+, oringinal doesn't run anyway, or it's on default-off ). Iran out of negatives when putting things back the way they were (I broke a couple of clips). Fridge was not cooling below 6 degrees C. on day 2 (30+d celcius about t though). I pulled it apart, again.
It seemed to be working day 1 until I tried moving cables
Anyway try and upstanding this (is it safe, I actually got negative reading on colder day (-4 in chiller, 4 in door).
Power to main +, and -.
Electric thermostat (ET) pos+ spliced to main + cable.
Neg- to - on danfoss.
ET neg- to P.
ET temp to thermometer then to t.
Fan pos+ Needs terminal in danfoss, fan - to F.
I joined c and t although now I realise my ET was plugged in and acting as control. Temp rage was 4-8.
Utilising p,c,t worked for me. I was actually looking for a fake neg for the ET.
Best eco setting for summer?
2.5c +/- 1.5c. Is it a a timing Here ? 4 mins, or is that a speed?
I'll clarify and try and upload my Nepalese power station (no offence meant, soz).
Tia

 

Daryl or anybody who could assist......do have any thoughts as to the make up of the Merlin Smart Speed Controller.....link below.
http://www.veco-na.com/images/Merlin_Smart_Speed_Controller_-_Instructions_-_7.26.11.pdf
Apart the power input, the only interface is between terminals C and T on the controller where the change in current varies the speed of compressor.

Bjorn

Looks like link is dead!

 

Looks like link is dead!

If you're offering any additional info/or asking a question bkc888, let's hear from you . We'd be more than happy to raise the 'dead'

 

Daryl or anybody who could assist......do have any thoughts as to the make up of the Merlin Smart Speed Controller.....link below.
http://www.veco-na.com/images/Merlin_Smart_Speed_Controller_-_Instructions_-_7.26.11.pdf
Apart the power input, the only interface is between terminals C and T on the controller where the change in current varies the speed of compressor.

Bjorn

Hi
I do realise this is a very old post however I enjoyed reading through and seeing what you created. I have fridge compressor that has failed.
I have a 370I ASU refrigeration unit on my boat.
Connected to the controller on the compressor is a red unit that is connected to a controller with a 3 position switch and thermostat. I have been trying to find a replacement for my controller and panel and the price for these parts are ridiculous. The item below together are close to 400 euro. I found on Amazon a temperature regulator that I have successfully installed.
amazon.es/dp/B0B7G8WZZR?ref=ppx_yo2ov_dt_b_fed_asin_title However it connects to the C and T terminals and as a result the fridge/Freezer is, I assume running at 2000 RPM. As a result due to the ambient temperature it is unable to reduce the Temp more than 1 Degree C. I am therefore looking for a speed controller that it seems you created. However there are some components you used that I am unable to identify. There is a Frigo component available however it has a potentiometer that needs adjusting with a screwdriver. As the boat belongs to an older Gentleman I want to make this as easy as possible. Ideally All I need is a switch that can be selected to alternative between 2000 RPM and say 3000 RPM allowing us to chase the freezer down low before going sailing and that we can return to 2000 RPM when we kill the engine. We are running at 12V. Would you be able to maybe suggest a very simple way in which I can rig a remote switch that is easy to reach. This is my alternative solution but not ideal given it is mounted on the Danfoss controller. Frigomatic speed regulator for Danfoss BD35 BD50 compressors using either 12/24V or 12/24V110-240V controller (penguinfrigo.co.uk)
Any assistance with how to easily modify my system further to give us a two speed option would be very much appreciated.

What I am replacing.

 

Can I refer you to previous post/s (namely,debe) which referred to motor speed change. If you check Danfoss DB50F specs, it will tell you that the resistance change between C & T will alter motor speed, ~700ohm, 3000rpm while 2000rpm, no resistor required.
Just curious why you're changing the Isotherm hardware ? Modification of current hardware may achieve what you are wanting. Maybe mark the rotating speed selector at 3000rpm/2000rpm positions or replace with 2 position switch with relevant resistor in circuit.

 

Can I refer you to previous post/s (namely,debe) which referred to motor speed change. If you check Danfoss DB50F specs, it will tell you that the resistance change between C & T will alter motor speed, ~700ohm, 3000rpm while 2000rpm, no resistor required.
Just curious why you're changing the Isotherm hardware ? Modification of current hardware may achieve what you are wanting. Maybe mark the rotating speed selector at 3000rpm/2000rpm positions or replace with 2 position switch with relevant resistor in circuit.

Hi! Many thanks for replying to my post. I realise it was a very old and might not get a response. The Fridge/Freezer box basically stopped working. I replaced the Danfoss controller and this did not resolve the problem and can now only assume it is the two Isotherm components as the compressor runs when I bridge C & T.
So as I understand it all I need to do is cut the cable going to C terminal and fit a three position switch. one position is via the 700 ohm resistor to C and the other direct to C? Can I assume that I still ignore the P terminal? Are all 700 Ohm resistors equal or do I need to specify a Wattage? My system is running on 12V.

 

I have an isotherm fridge and I bought their smart controller that varies the compressor speed according to the delta between setpoint and actual. It also reduces the setpoint so the fridge gets colder when it senses that battery is charged above a certain level to dump excess power from solar/shore power into the fridge and so preserving battery power later when shore/solar goes away, eg at night. All this works as designed, the issues with it is the potentiometer for adjustment is in the fridge and its guesswork setting it, and the parameters are set by dip switches on the thermostat, there is no display either, I have an analog thermometer in the fridge instead. I would like to improve on this design to have it controlled with a microcontroller to allow me finer control and better monitoring. Then a PID controller can be used to maintain the setpoint.

My thoughts are that the compressor speed may be able to be set continuously variable via pwm. The bd35f datasheet lists the various resistances and compressor rpm along with the current in mA that flows between the C and T terminals. If pwm is problematic a digital potentiometer could be used instead. I can measure battery voltage to achieve the desired functionality of dumping excess power to drop the temperature to 2 or 3C instead of 5 or 6C. Additionally add another temperature sensor to measure heat at the coils outside the fridge to control the fan speed for cooling that to minimise noise and wear etc. My fridge is in a campervan so excess fan noise at night is annoying.

I found this thread while I was looking at digipots or what pwm would be needed, specifically what the voltage is on the C T terminals at various compressor speeds. I think I will just pull the fridge out and measure it. Then maybe disconnect the existing thermostat and insert a microcontroller to see whats needed.

 

The resistors vary the current betwean C & T for different speeds.

 

Hi, i'm new to this. MY Waeco, with Danfoss BD50F compressor, got sea water in the electronics, and the 220v packed up. I took all electronics out and connected straight to 12v with a standard mechanical freezer thermostat. It worked well, but the thermostat started playing up so installed an electronic thermostat to it, not realizing that it fed 12v into the thermostat circuit C & T. It has now stopped working, even if I bridge C&T.
Where do I start looking?
Is there an easy answer? or bypass? I am not an electronic fundi, and it's too expensive to replace the controller on an 18 year old fridge?

 

Hi, i'm new to this. MY Waeco, with Danfoss BD50F compressor, got sea water in the electronics, and the 220v packed up. I took all electronics out and connected straight to 12v with a standard mechanical freezer thermostat. It worked well, but the thermostat started playing up so installed an electronic thermostat to it, not realizing that it fed 12v into the thermostat circuit C & T. It has now stopped working, even if I bridge C&T.
Where do I start looking?
Is there an easy answer? or bypass? I am not an electronic fundi, and it's too expensive to replace the controller on an 18 year old fridge?

Keep an eye out for dumped port fridges, apart from Engel nearly all other fridges use the same compressor controler. After colecting a few fridges from a scrap yard i found a couple of good spare controlers, saves buying them.