Go Down

Topic: Arduino Power Supplies (Read 3283 times) previous topic - next topic

oric_dan

Quote
Your litany of disasters with approved stuff makes me feel even better about buying unapproved stuff, especially if I can get it really cheap.

Not sure that was the intent....

I would call it irony, but lefty would probably call it sarcasm, and who knows what doc.e
would call it.

Quote
I wonder to what extent I cooked the mineral oil and the compressor - it was way too hot to touch.

mineral oil ... ???

retrolefty

#31
Dec 09, 2012, 10:52 pm Last Edit: Dec 09, 2012, 11:00 pm by retrolefty Reason: 1
Well I'm anxiously awaiting the arrival of my new Arduino power supply, sans any UL approval or not. Approved by Haruyrkb and it's $11 + free shipment is good enough for me. 20 watts max output power, displays input and output voltages and output current draw. Adjustable current limit 0-2amps and adjustable output voltage .93-20v (stepdown ), it's a tinkers delight.
Lefty
http://www.ebay.com/itm/170929163665?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649



Constantin


I would call it irony, but lefty would probably call it sarcasm, and who knows what doc.e
would call it.
I guess the smiley face was not enough of a hint. Ok. Time to move on.

Quote
mineral oil ... ???

Most refrigeration systems use oil to keep the compressor lubricated. Said oil circulates with the refrigerant. Oil and refrigerant can decompose and burn up if the temperatures inside the sealed system get too high. Once they do that, they become acidic and start to attack the sealed system from the inside out.

Even on approved equipment.  :)

Constantin

Hey lefty that is a nice looking board. Look forward to hearing how it performs.  Limiting the current that is fed into the arduino is one way to limit its magic smoke potential? 

retrolefty

#34
Dec 10, 2012, 12:14 am Last Edit: Dec 10, 2012, 12:27 am by retrolefty Reason: 1

Hey lefty that is a nice looking board. Look forward to hearing how it performs.  Limiting the current that is fed into the arduino is one way to limit its magic smoke potential?  


Yea it's cute alright. It still brings up that argument about what constant current really means and what is a CC/CV supply. I have stated (correctly I might add  ;) ) that a supply like this should not be called a constant voltage/constant current supply but rather a constant voltage supply with an adjustable current limit where it will gracefully decrease (foldback) the output voltage to maintain the adjusted current amount if faced with a decreasing load resistance. Example is if you set this to 10 volts output and 1 amp current limit and then wire a short to the output terminals you will still get a steady 1 amp current flow, but most certainly won't see 10vdc applied across the wire!
Alternately if you remove the wire and replace it with a 20 ohm resistor you will not then get a constant 1 amp of current flow but rather only 500 ma, so nothing constant current about that, just automatic current limiting action when the load resistance forces it into that mode.

Now that is not to say you can't operate it as a constant current supply for say a 350ma power led, you just set the current limit to 350 ma and set the output voltage well above the Vf value of the led and the power supply will stay in it's current limiting mode forever and will raise and lower the output voltage to any changing load condition of the LED.

So I guess you can say it can operate as a constant voltage supply or as a constant current supply, but just not at the same time, ohms law still wins.

Lefty

oric_dan

Quote
Well I'm anxiously awaiting the arrival of my new Arduino power supply, sans any UL approval or not.

Nice looking little supply. Good find, I may even buy one myself, and I shouldn't expect to
find an Approval Agency sticker on something that isn't intended to be plugged directly into
the power mains [you wouldn't, would you?].

Question: if you plug a 24V, 2A supply into 120V, doesn't that turn it into a 10A Supply?

Quote
a supply like this should not be called a constant voltage/constant current supply but rather a constant voltage supply with an adjustable current limit

Hey, if it says constant current, doesn't that approve it as constant current?

Quote
mineral oil ... ???
Most refrigeration systems use oil to keep the compressor lubricated.

mineral oil ... ???

Constantin

Whoops, forgot that this is a R134a based unit. In that case, its most likely POE oil. But yes, there is oil in there. We get to drain it at work and dispose of it as a hazardous substance.

Older units using R22 and similar refrigerants would have been using mineral oil.

Go Up