Electronic constant current DC load

[MJLorton]

The drill bits came from Builders Warehouse...just over R1000 for the three.

The FET and Resistor were just placed there for orientation...if you look close enough at the resistor in the final picture it has heatsink compound underneath it. The case of the resistor is isolated from the terminals (I have just checked to confirm that) so no need for mica there.
I do have mica strips for the under side of the FET. I was going to use a piece on the top, under a washer to isolate...and do something to isolate the shank of the bolt...

Yes...metric taps for the next project...   

[btfdev]

Hello all

During the holidays our team also got our own dummy load built.

Vishay IRL520 logic level MOSFET
Texas Instruments LM324N Op-Amp
Hopesun PM-2 Ammeter
Bourns 3540S-1-103 10-turn 10K pot
Riedon PF2470 TO-247 power thin film resistors

We have captured some pictures and they are on our website photo journal page.

http://www.binarytaskforce.com/photocontact-album-13

Cheers, Team BTF

[MJLorton]

I managed to have some chill time today and continued to tinker and I'm just about have the enclosure complete...

I hope to have the assembly and wiring complete this weekend.

[SeanB]

Like the safety sandals there Martin.........

Though those vent holes were part of the moulding of the case, well done with getting them all so nice.

[MJLorton]

Like the safety sandals there Martin.........

Though those vent holes were part of the moulding of the case, well done with getting them all so nice.

Yes, carbon fibre reinforced!   
...part of the moulding....not...courtesy of some great CAD drawings and some painstaking drilling 
 

[MJLorton]

Ok...almost there!!!!

Started assembly...had hoped to complete it this weekend  but...I had still not decided how I was going to power the panel meters....

I decided in the end to go with a DC to DC converter which I have now ordered form RS so I should have it all together next weekend.

[SeanB]

Looking good there Martin.

[MJLorton]

Finished at last!

Here is the link to the final video: https://www.youtube.com/watch?v=afM1aujgAF8

I'll post some pics here and follow-up with the CAD drawings, final circuit and parts list soon.

[Billy]

Looks excellent, very well crafted. Well done.

[btfdev]

Hello all

Previously mentioned before, during the holidays we got our own dummy load built.

Vishay IRL520 logic level MOSFET
Texas Instruments LM324N Op-Amp
Hopesun PM-2 Ammeter
Bourns 3540S-1-103 10-turn 10K pot
Riedon PF2470 TO-247 power thin film resistors

Provide a quick write up here.

http://www.binarytaskforce.com/Weblog/2013/02/08/dummy-load/

Cheers, Team BTF

[jwrelectro]

Martin I know you put a lot of work into that el-load and good job!  You mentioned in the video that with your max current limit set you did not get to use the full range of your course current adjustment control.  May I make a suggestion to look at my full schematic in this thread and see how I implemented this feature.   I think you may only need to move a couple of wires on your unit so that the max current limit comes after the course current adjustment and not before it.  This way you will get the full range of that control no mater where the max current limit is set because you are then simply scaling the control voltage to the opamp.  I haven't seen your updated diagram so I might not be correct.  Anyway great job and that was a good detailed review in the video.

[MJLorton]

Martin I know you put a lot of work into that el-load and good job!  You mentioned in the video that with your max current limit set you did not get to use the full range of your course current adjustment control.  May I make a suggestion to look at my full schematic in this thread and see how I implemented this feature.   I think you may only need to move a couple of wires on your unit so that the max current limit comes after the course current adjustment and not before it.  This way you will get the full range of that control no mater where the max current limit is set because you are then simply scaling the control voltage to the opamp.  I haven't seen your updated diagram so I might not be correct.  Anyway great job and that was a good detailed review in the video.

Thanks very much for the feedback John. Heavens...I read your post twice (bit of a head cold...) thinking "what have I done..." but now I realise what you are saying and you are correct...I'm "wasting" many turns on the coarse adjustment pot.
I will investigate soon!
Cheers,
Martin.

[MJLorton]

Looks excellent, very well crafted. Well done.

Thanks Billy.

[MJLorton]

Here are the CAD drawings of the enclosure.

Thanks very much to Yves (forum id: Yttrium) for doing the enclosure design work and providing great guidance along the way.

Please note that these drawings are for non commercial use only.

Parts list:

* Infineon MOSFET N-channel 200V 13.5A TO-220 - BUZ31L H
* Vishay 534 Series Pot with 6.34mm shaft, 50K
* Vishay 534 Series Pot with 6.34mm shaft, 5K
* 10 turn 10 k trim potentiometer
* 1uF 50 volt electrolytic capacitor
* Arcol HS50 Al house wirewound high power resistor,1R (1 ohm) 50W - HS50 1R J
* National Semiconductor Quad op amp, LM324N 1MHz DIP14
* LM7806 voltage regulator
* TRACOPOWER, TMA1212S, unregulated DC-DC,12V 1W - (isolated power for the panel meters)

Cheers,
Martin.

[Mr Eastwood]

Very nicely done!