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My constant current load - 90W , 3A 30V

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grenert:
Jay_Diddy_B,
Did that case come with the heatsink?  Where did you find it?
Thanks!

Spikee:

--- Quote from: rbola35618 on February 26, 2013, 01:31:03 pm ---Nice video and projects Spikee  :-+.

--- End quote ---
Thanks!


--- Quote from: grenert on February 26, 2013, 03:20:48 pm ---Jay_Diddy_B,
Did that case come with the heatsink?  Where did you find it?
Thanks!

--- End quote ---

He used an off the shelf case. Got a metal plate the same size as the normal end cap. Drilled some mounting holes in it and mounted the heatsink on the plate.

Jay_Diddy_B:
Hi Grenert,

Spikee is correct. Here are the details:

The case was manufactured by Hammond part number 1598A.

The rear panel was cut from aluminum sheet 0.062, 1.5mm.

The Heatsink was cut from a length of aluminum extrusion. It is about 1 inch (25mm high)

I drilled and tapped the heatsink to attach it to the metal plate.

This design is good for about 10W dissipation.

Regards,

Jay_Diddy_B

clcham:

--- Quote from: Spikee on February 25, 2013, 02:55:32 am ---So i had some more time and i worked on the constant current load.

I have fitted 4 IRFP064N on a Hyper z600 CPU cooler and used one opamp for each mosfet. As a load resistor i use 0.1 Ohm 3W now but i will be switching them for 8 W equivalents. I will be testing the supply whit a 200W load tomorrow. But i already peak tested it at 63A , 10V = +-630W but some wires , shunt wattage etc was to low to run it for longer than a 5-10 seconds. This setup should be capable of 200W whitout getting hotter than 50-60 deg C. using one 120mm fan which has an resonable CFM. I can fit another fan to improve it ... but i have to make the pcb first. I need to get some connectors so i can hook up my 750W coolermaster pc power supply and see what the max of this cooling setup is. I think it is about 300-400W and then it will probably be around 60-80 degrees C.

Sorry for the bad photo's / video my phone was empty and it is really late now ... but i'm just soo exited  :o

Pic of setup:
https://dl.dropbox.com/u/100819959/constant%20current%20load/20130225_032839.jpg

Breadboard:
https://dl.dropbox.com/u/100819959/constant%20current%20load/20130225_032825.jpg

Feedback + gate wires:
https://dl.dropbox.com/u/100819959/constant%20current%20load/20130225_032828.jpg

Close-up of resistors , mosfet construction:
https://dl.dropbox.com/u/100819959/constant%20current%20load/20130225_033010.jpg

Todo:

-Make pcb
-Bigger wiring on some places
-Add intelligence (STM32 + touch screen lcd)
-total current measurement (LT6100 whit 2m ohm shunt)
-Put in an enclosure
- ...



--- End quote ---

Hi Spikee, I've seen your schematic, I have a few questions:
1) why do you need a pull down resistor?
2) there is a 2.7k resistor in the feedback path, what is it for?
3) what is the maximum voltage capable of discharging with this design?

thanks

Spikee:
1. So the mosfets turn off when you apply no current.
2. Probably some kind of filter (haven't looked at schematic , there is probably also a cap somewhere)
3. It is limited by the voltage of the mosfet. The IRFP064N has a VDSS = 55V . If you need more then you need to change the mosfet.

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