| Electronics > Beginners |
| DIY power supply |
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| Doctorandus_P:
Turn it around. What sort of things do you do with electronics? Then make a power supply for those things. You like electroplating? You may need 3V @ 100A. You like microcontrollers? 3V3 and/or 5V is all you need. You like opamps? A dual supply of + and - 15V will be handy. You like motors? You want lot's of amps from a simple unregulated power supply. An important feature for any lab power supply in my opimion is an adjustable current limit. 30V 3A was a sort of standard for 40 years, but electronics has changed a lot and those power levels are hardly ever needed anymore. If you want to design something yourself and want to keep it cheap then I suggest to keep your goals within reason. 20V @1A will be a very usefull power supply and designing such a power supply with adjustable voltage and current limit wil give you plenty to do for a few months of spare time. There are at least 2 different very common kits with adjustable voltage and current limit you have to solder yourself from China in the price range of < USD 10. If you complement those with voltage and current meters you have a quite decent power supply. DPS5005 is step down only. However the DPH series from the same manufacturer can also do step up, some go up to 80V. They also have simpler designs with 7-segment display's and push buttons instead of a TFT and rotary encoders for a price of around USD12. |
| Old Printer:
--- Quote from: rdl on August 03, 2018, 04:52:35 pm ---Too bad you're not in the US. My recommendation for a beginner power supply is one of these: They cover just about all beginner needs and are commonly found on ebay for $100-150 used. I would look for something similar as far as features and specs. --- End quote --- Ditto on this, but I will add that this same PS was also sold by BK Precision as their model 1651. The ITT tech schools that went bankrupt a few years ago unloaded pallets of these on the liquidation market. This is a very solid PS and very easy to work on, and no fan so it is quiet. Tektronix just rebadged it, but in the process put together a very good service manual with full circuit description, troubleshooting, schematics and parts list. The manual is available on CD via ebay for about $12 and the scan is very good quality. In the last few months I picked up 3 of the BK flavor for under $35 each. One had a fault in the B supply, I got TEK's SM and tracked it down to a bad 10 cent diode. The seller replaced the PS for free and told me to keep the bad one :) I learned a lot tracking down that diode. Bottom line, the BK's are ugly compared to the TEK's, but are available far cheaper and it is the same hardware in a different color case. |
| Pirateguy:
--- Quote from: Jwillis on August 04, 2018, 05:33:49 am ---Oh let him have his fun. 40 volts and 5 amps can be a tough nut to crack if using BJTs .Power BJTs safe operating area drops off a lot over 30 volts so even the trusty 2N3055 is only capable of a couple amps flat out at 40 volts .That can shorten the life of the transistor. So if you want them to last you'll have to parallel 4 or 5 to keep the things cool. MOSFETs don't respond well to linear applications but can handle much more amperage when pulsed. Are you going to use MOSFETs or BJTs.Of course this is assuming you would like to build from scratch.Most PSU circuits on the web will only go to 30 volts since most regulators are really only capable of around 35 volts .Even the lm317 has a max rating of 37 volts.There are regulators that go higher like the TL783 if your looking for direct regulation. If I may suggest a floating regulator like the LM723 or similar .They tend to be much more stable and are easier to use.There are others that use op amps as well . There are hundreds of ways to build a PSU .It just depends on how complex and how modern to want it to be. --- End quote --- indeed let me have my fun! that's a big part of the motivation behind the elaborations. but also my projects are really all over the place. i do work with arduinos from time to time, battery operated devices using all kinds of cells, but i also screw around with jacob's ladders and recently i have gotten a bit obsessed with tesla coils, particularly small ones. and then i'm also gonna be messing with low voltage AC when i get around to playing with this EL wire i have, and now recently i have been looking at diy spot welders. my main focus though is on special effects for miniature dioramas, and for this i am looking at pretty much anything i can get done at a low cost, incl; various high voltage spark thingies like the marx generator, and i want to see how small i can make a plasma ball, ultrasonic foggers to animate liquid, electromagnets to mage items float in midair, tiny animatronics, floating water drops using a strobe, etc etc. so yeah, variation is desirable. and no i will not be building from scratch. though i might do something similar from scratch for a specific project some time. atm i am thinking of taking this approach: step 1: build basic PSU out of old ATX psu with a single output that switches between the different voltages available from the ATX. (-12 and -5 are on there, so why not inculde them) along with a volt/amp display and a temperature display. possibly later i will expand this above 12v with some boost converters or something. (so far everything should fit into the original ATX housing.) step 1b: add a dedicated usb port or 2 on front and/or a series of them on the rear of the unit. step 2: build second half of this unit in the form of a 317 based variable supply along with another volt/amp display. i may use a different source for this, like the 32v 1.5A PSU i have (a particularly nice one from HP with lots of safety features) in which case i would need a larger housing. step 3a-z: over time add more features to the larger housing such as an AC output, func generator/pwm generator, dummy load, second temperature display (for ext), etc. step 4: maybe integrate a ZVS driver in the thing. i imagine this taking place over the course of a year or 2. |
| Pirateguy:
on the topic of function generators, i do have some ICL 8038 ICs that i could build one with. i also have various arduinos and one of those cheap arduino starter kit LCD displays, as well as a small tft screen. how would u rate the challenge level of such a project? incidentally i have put together that XR2206 thing and BOY does it suck! lol i might try to implement those improvements in those videos posted, but i'm not sure it's worth it. prolly end up using it in some project for some specific task or something... |
| Jwillis:
Sounds like you have a version 1 ATX.Version 2 has no -5V. A simple rotary switch would work or individual output terminals up to you .A variable supply can be wired from the -12v and +12v and common ground using split rail regulation.Check around for split rail PSU or you can get assembled + and - adjustable power modules on Ebay. But you will only get the maximum current available of the Negative rail (-12V). Or just use an adjustable module from the +12V and common .The USB can be wired directly from the +5V and Com. A simple digital volt meter ,amp meter and temp meter with sensor can be powdered from appropriate voltage source .Either +12V and common or +5V and common check the meters specifications. If you intend on a high voltage output I would keep that as a separate isolated output from the low voltage outputs.I would even go as far as a separate transformer .There are modules available based on the TL494 IC that run off of 12VDC .These are low amperage from around a few micro amps to a few milli amps. The sense wire on the ATX just needs to be switched to ground to turn the unit on usually a green wire but check the pin outs for your specific PSU.All the same polarity and voltage wires can be tired together. Yellow for +12V .Blue for -12v.Red for +5V, white for -5V and orange for 3.3V .Black wires are ground . Grey wire can be tied to a LED and resistor to indicate the unit is on.Again check the pin outs for your specific PSU.Wire colors may be different. The total current available is dependent on the ATX. I've not seen version 1 ATX power supplies over 500W. |
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