Danfoss Compressor Speed Controller

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.
 

Thread Starter

RVRepairer

Joined Dec 28, 2015
6
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.
 

SCOOTER68

Joined Dec 13, 2016
2
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
 

SCOOTER68

Joined Dec 13, 2016
2
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 ??
 

St Joseph

Joined Feb 19, 2017
3
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?20170216_220912.jpg
 

debe

Joined Sep 21, 2010
1,179
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.SWITCHING MOSFETS.JPG CIRCUIT BOARD.JPG CIRCUIT.1.jpg CIRCUIT.2.jpg
 

St Joseph

Joined Feb 19, 2017
3
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.
 

debe

Joined Sep 21, 2010
1,179
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.
 

St Joseph

Joined Feb 19, 2017
3
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
 
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