Electronics > Beginners
lab power supply
EEVblog:
--- Quote from: tooki on December 15, 2019, 12:47:22 pm ---So while it might have always been envisioned in your mind as the uSupply, anyone watching the PSU series from the beginning (as I did) would see it as morphing from a more traditional PSU design into the uSupply. And for sure, for someone looking for how the “lab PSU” series continues, it’s not self-evident from the video titles that the uSupply is the continuation. Looking for “PSU part 14” comes up dry.
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These prototypes must be a figment of my imagination.
From left to right, dated 7/8/09, 3/5/10, 31/8/10
I showed that first prototype to Leo Simpson at Silicon Chip when he visited Altium in 2009 and dropped by my cubicle to say hi. Almost got it published in SC, but I just kept fiddling with it.
EEVblog:
--- Quote from: Calvin on December 15, 2019, 12:35:28 pm ---Would You mind to elaborate on the issues of the LT3081.
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Sorry my memory of the exact issue is rusty. Something to do with back diode protection killing the chip. I wasn't the one that found it.
I think there was talk on the forum at the time whether LT would recall the chip.
MarkF:
--- Quote from: EEVblog on December 17, 2019, 11:12:47 am ---
--- Quote from: Calvin on December 15, 2019, 12:35:28 pm ---Would You mind to elaborate on the issues of the LT3081.
--- End quote ---
Sorry my memory of the exact issue is rusty. Something to do with back diode protection killing the chip. I wasn't the one that found it.
I think there was talk on the forum at the time whether LT would recall the chip.
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LT3080 wierdness - dave's power supply (eev224) gone mad
glinjik:
update and question so after advice from
--- Quote from: Jwillis on December 17, 2019, 08:03:36 am ---What is the voltage rating of your electrolytic capacitors and The voltage of your transformer secondary.
If you measure the AC voltage of the secondary you take that measurement and multiply by 1.4 to get the rectified voltage With filter caps . So for example if your transformer is putting out 12VAC . 12 X 1.4 = 16.8 VDC after rectification and filter caps . 16V capacitors will be right on the edge of destruction at that voltage. Try to double the capacitor voltage rating over the rectified voltage. Don't just take the voltage of the rectifier and try to match the capacitors to that voltage because as soon as you put a filter capacitor in circuit that voltage will rise potentially exceeding the rating of the filter caps your installing . If you can salvage old televisions there are usually some big high voltage ones in those . For your simple power supply a couple 220uF or 470uF 200 - 400 V capacitors would be more than adequate.
If your going to parallel transistors you need to bias them to prevent load hogging and thermal runaway. Usually this can be done simply by putting a resistor at the base and a very low resistor ( 0.1 ohms is plenty) with a high wattage (5W) at the emitter of each transistor. Even in a single transistor circuit, biasing will keep that transistor from exceeding its rated current capability if the power supply is over loaded by shorting .
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i installed a 450v 150mf cap and that seems ok my little melt down did destroy both 2n3055's what im thinking now is no load i get a steady22.02v under load it drops to 19.59v its only a 12v led light as a load what im wondering is this can it be made more stabe? the variable resistor pot at P3 does nothing for caibration of volt meter im using a digi one im guesing that pot was designed to calibrate a analogue version also if i connect volt meter as per diagram it only shows 9 volts? maybe volt meter should be connected direct to output? can i get rid of c8,c9.d10.r8p3 amnd c10 and put a big output filter cap there instead i know a lot of questions and you all prob think im a thick noob but im loving this project :)
glinjik:
also want to incorporate this fan control
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