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Author Topic: Dummy Load  (Read 648 times)
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WeSo
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« on: April 30, 2017, 04:18:12 16:18 »

Hello,

It's my first post and I think that one of the best ways to indroduce myself is sharing. I will try to share and learn from each other.

This project is simlple, the idea was to do a dummy load for test other circuits. I used a dsPIC30F2010 as controller of it, sensing the current with an external current monitor with analog exit. Besides, it has temperature control for protect the MOSFET.

The limits are up to 30V and 3A.

You can see all the files here: https://github.com/JDGon/DummyLoad/

A picture:


I guess that you like it. Any suggestion is wellcome!
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Gallymimu
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« Reply #1 on: April 30, 2017, 05:33:13 17:33 »

how fast can it respond to source transients?  i.e. how fast/stable is the control loop?
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WeSo
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« Reply #2 on: April 30, 2017, 05:54:40 17:54 »

how fast can it respond to source transients?  i.e. how fast/stable is the control loop?
The PIC puts a PWM signal (integrated), and the current is stabilized with an OPAMP with feedback (there is a shunt resistor). I use the LMC662 with a slew rate of 1.1V/us.

The first tests were success, but I don't have captures from my oscilloscope right now.
« Last Edit: April 30, 2017, 06:04:58 18:04 by WeSo » Logged
WeSo
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« Reply #3 on: May 02, 2017, 01:20:54 13:20 »

By the way, I have some extra PCB (without components) in my drawer. I don't think I will use it, and maybe it could help someone.
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zed65
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« Reply #4 on: May 03, 2017, 10:33:04 22:33 »

Nice little project, but why the quite hefty dsPIC30F2010?
What are the other main components you are using (MOSfet, DAC, opAmp)?
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WeSo
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« Reply #5 on: May 03, 2017, 11:38:16 23:38 »

All components are in the schematic, but I can sum it up:
MOSFET: CSD18502KCS
OpAmp: LMC662
Current monitor: INA250
Display 7-seg controller: SN74LS247
Temperature sensor: LM35 (a classic)

Yes, maybe dsPIC30F2010 is "oversized", but I like, for example, the option for the encoders. Besides I had it from other old project  Grin
It was a small project, but I thought it might be useful to test some circuits, especially those with "sensitive" power supplies.
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sphinx
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« Reply #6 on: May 04, 2017, 12:00:46 00:00 »

would be nice to have a dummy looad to test my power supplies, how much are you asking for the pcb ?
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WeSo
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« Reply #7 on: May 04, 2017, 12:05:16 00:05 »

The PCB it's free (only pay the shipment), I want to contribute to the community. I think that I have 1 or 2 more, but if there are people interested, we can order more.
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sphinx
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« Reply #8 on: May 04, 2017, 11:56:06 11:56 »

i am in for one just tell me how to send you the shipment.
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WeSo
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« Reply #9 on: May 04, 2017, 04:46:46 16:46 »

Only one little thing, due to an error with a transistor footprint, the dummy doesn't work using the USB power. This can be easily fixed changing two traces, but I prefer power it with the DC jack.

If it doesn't matter to you, send me a PM =)
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