Wanted budget power supply - Page 1
Forum section: electronics / general

author: Raj
author_rank: Frequent Contributor
timestamp: September 22, 2018, 03:31:09 pm
content: Looking for a power supply, withunder 120 USDatleast upto 15volts out(well 13.8 is fine for now. don't need regulation on any application going above that voltage so can use variac instead)5amp capabilityfine voltage controlcurrent limitlow or no cooldown time ( should be able to run for a long time without overheating,thus leading to thermal safety to trigger a shutdown)low rippleFrom a good companyaccurate display (can add a display later)Could have made a lm 338 based one but those run quite hot at amps as low as 1A plus I don't wanna work my brains out looking for best power transistors and input dials and indicator displays, when I have the money.

author: sn4k3
author_rank: Frequent Contributor
timestamp: September 22, 2018, 04:38:15 pm
content: Look at Korad KA3005P or Korad KA3005D, it's inside your price range and good for it price. Also at that price there aren't that many chooise to go.That power supply is programable and with presets, you can choose the current and voltage before turn on the output.

author: Raj
author_rank: Frequent Contributor
timestamp: September 23, 2018, 04:34:58 am
content: Quote from: sn4k3 on September 22, 2018, 04:38:15 pmThose look good.How good are they? It seems a bit overbuilt yet spikey when turned on( as describes in buyer review) but I kinda like your suggestion.I've herd many people, specially HP users, have killed their lasers because they set a setting then turn the supply on, and the initial spike kills it.I was also looking at bk precision 1550 but it too looked like cheap cra# being a switching supply. Also it overheats and is plagued with spikey-nessI wonder how Dave (admin's) power supply project is going and how expensive it's gonna be.I'll be more liberal and consider good kits too.

author: Raj
author_rank: Frequent Contributor
timestamp: September 23, 2018, 10:41:06 am
content: I was thinking. What if I buy a fixed power supply and drop it's voltage using extra circuitry?Need a suggestion for a clean and efficient way of doing it. As far as I know, most methods will be inefficient (like regulated power dropping) or will introduce ripples and spikes (buck converters) which I can't even test because I don't have an oscolliscope.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 23, 2018, 02:37:42 pm
content: Dont go there ... tweaking and fiddling / playing with controls lines / feedback lines can do more harm on your equipment.Use proven and reliable linear models brand with ocp ovp short overheat protections ... If you hate the heat as you wrote, go with proven reliable SMPS model / brand, avoid china stuff.At 15volts and 5 amps you already have 75watts of heat dissipation.Why ? digitally controlled ones may lack speed of reactions / feedback control on some types of loads ...Played with Lambda LLS and LMS series, they where old in the architectures, motorolla hc08 cpu series, very loud and noisy fan, but very stable and rock solid, but pricey ..Cheap china buck boost models aren't isolated on the outputs until you use and transformer based supply to feed them, and when they fail, it can get ugly.Smps have less noise on the output, less heat dissipation, but tend to have bad reactions on certain types of loads ... unless having good / industrial models = priceyMastech ang GW Instek or any cloneshave many control quality issues, fully check them before playing with them, had many smps ones failed in the mosfets stages ... the linears models almost never failed, 1 bad relay changed once, some linear models have relays to limit the heat dissipation, nice feature.my 2 cents experienceon a side note :Purchased out of curiosity an Kikusui PAD model, they are based on SCR bridge rectifiers instead of an standard rectifier bridge ... they can output tons of watts with an small footprint, very low noises, low heat dissipation and very good protections1u rack mount chassis can go up to an 1K Watt, some Sorensen, Xantrex, Power Ten, SCR models are based on the same principle.I use an old Kepco ATE75-8 psu, an 57 pounds baby, recapped entirely, added 4 1/2 digit panels dmm instead of needle meters, changed the original pots to 10 turns pots was the greatest idea,modded the fan to an thermally controlled one helped a lot, you dead short this puppy and have an wonderful 864watt heater in your room loll, it was running very loud. You have to know what you're doing ... i have the schematics.And most importantly of all, be sure you can get an service manual just in case of ....

author: coromonadalix
author_rank: Super Contributor
timestamp: September 23, 2018, 02:57:20 pm
content: You may find some Astron / Pyramid linear models, they are easy to hack in some case for variable voltages, but have fixed current limit to an maximum value, they are often based on lm723 ic's, adding an variable current limiter is very tricky.Had busted a few chips designing my own pcb version while retaining the main transformer and rectifier filter section ...Once again having the service manual help a lot.Not sure in India what you can find, to help you ??Good luck

author: Raj
author_rank: Frequent Contributor
timestamp: September 23, 2018, 03:53:57 pm
content: Quote from: coromonadalix on September 23, 2018, 02:37:42 pmHoly cow, That's one heck of a power supply (500wt I guess?).Lucky you, I don't even have enough space to keep it.Analogue is fine for me, as long as it is stable and I can add display later.maybe I should strike that off of my requirements listI'll be ok without digital control as long as I have multiturn dials

author: Raj
author_rank: Frequent Contributor
timestamp: September 23, 2018, 04:00:25 pm
content: Quote from: coromonadalix on September 23, 2018, 02:57:20 pmThanks a lot. But I do have paypal and canadian bank cards and relatives in Australia, Canada and U.S.Pyramid ones seems quite skookum goodDropping the 15v requirment to 13.8v

author: coromonadalix
author_rank: Super Contributor
timestamp: September 24, 2018, 03:31:34 am
content: Pyramid are standard psu, BUT they dont offer very much gadgets like ovp ocp etc ... i think they all use lm723 ic's, the schematics are in the users manuals, you can find them relatively easy ...Just the current part is fixed, you can find tons of lm723 ic's designs on google ...something like this :https://www.eleccircuit.com/0-70-volt-2-amp-dc-variable-power-supply/or its brother with an ovp circuit you have to reset to get it going againhttps://www.eleccircuit.com/power-supply-regulator-0-50v-2a-by-ic-lm723-transistor-2n3055-bd140-a671/You have some linear DIY pcb with all the parts on Ebay, as low as 5 $ usdhttps://www.ebay.com/itm/Red-0-30V-2mA-3A-Continuously-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-PCB/201751652278This one seems very nice, feature packed, schematics available, Strange resemblance with mastech GW Instek psu's ??https://www.ebay.com/itm/Continuously-Adjustable-DC-DC-Regulated-Power-Supply-DIY-Kit-0-35V-0-5A/173417145714?hash=item286077a572:g:VKMAAOSwHt1bTujtThey are cheap enough with good features, it just need the main input x-former diode bridge and main capacitors

author: Raj
author_rank: Frequent Contributor
timestamp: September 24, 2018, 05:01:10 am
content: Thanks.I'll look around for a good kit

author: Raj
author_rank: Frequent Contributor
timestamp: September 24, 2018, 07:28:19 am
content: How about not having the current regulation built in, for an external current regulator? What are my options then?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 24, 2018, 02:07:30 pm
content: Well if you do build, repairs things etc ... the current limiter is an obligation to have ...It depends of the psu you find, some of them as i said can be safely hacked of can be made variable ...The Ebay links i gave you are enough for a start ...Here's an link to an variable current and voltage DIY psuhttp://electronics-diy.com/30v-10a-variable-bench-power-supply.phpYou have an thread here :https://www.eevblog.com/forum/projects/lm723-and-variable-current-control-technique/The circuit 3 design is very good, and doesn't cost a fortune in parts,but you have to get an ammeter with an shunt in itaround 0.2 ohms i think, to be in the 3 amp current range, (for the current limit, pins 2 and 3 of the lm723, you have to get around 0.6v -0.65v between those pins)

author: Raj
author_rank: Frequent Contributor
timestamp: September 24, 2018, 02:25:07 pm
content: excellent

author: coromonadalix
author_rank: Super Contributor
timestamp: September 24, 2018, 11:18:41 pm
content: For the circuit number 3 they use an power diode to create an minimal drop of voltage, you can replace the ammeter with the 0,2 ohm resistor i've talked earlier.With the diode and the power resistor, you have the chance to set an minimal current output and a maximum ...Here's an slightly corrected version with an power resistor if you don't have an ammeter with an integrated shunt, you can add an small meter in parallel with the power resistor with a small trimpot to adjust the read value.I use almost the same variant for one of my old 10 year psu project.The only problem / drawback left is : the psu wont start a zero volts, the lm723 specs will start a 1.2 volt and up.

author: Raj
author_rank: Frequent Contributor
timestamp: September 25, 2018, 02:35:20 pm
content: ordering parts. should take 3 months to arrive.i'll also read lm723 datasheet meanwhile

author: sn4k3
author_rank: Frequent Contributor
timestamp: September 25, 2018, 04:06:21 pm
content: Quote from: Raj on September 25, 2018, 02:35:20 pmYou also have DPS5015 modules, using with a good power supply you are able to do 48V at 15A. I don't like the interface but these things works, and as bonus they can be remoted operated.DIY is easy to go wrong, special in this case when you are dealing with mains and power to feed your things. If you build that be sure to follow and carefull test your finish result. Also don't forget a enclosure, in metal if possible, so in case of fire it will delay a big disaster

author: Raj
author_rank: Frequent Contributor
timestamp: September 26, 2018, 10:42:07 am
content: Those modules are good but not good enough for my case.Been doing mains work a lot. In-fact, I must have dealt with mains voltage more times than safe voltage. Thanks for the concern. Also all my project have had laminated core transformers until 2015, when smps became cheaper. They are also efficient.Usually I use aluminium box for project so as to reduce magnetic interference.i'll get a dps module someday for other applications.

author: VEGETA
author_rank: Super Contributor
timestamp: September 26, 2018, 11:01:46 am
content: Make your own is better for you. Start with this module for example:https://www.aliexpress.com/item/AC-100V-240V-To-DC-36V-Switching-Power-Supply-Board-AC-DC-Power-Module-36V-5A/32898292916.htmlThen after it, connect a DC-DC buck converter module to get something like 0-36v (or 0-24v) which is gonna be your PSU. You could put LM317 module if you want linear output but it is only 1.5A.Use a good case for this project + a nice cheap panel meter. I will do the same on my video blog soon enough.regards,

author: coromonadalix
author_rank: Super Contributor
timestamp: September 26, 2018, 02:57:34 pm
content: I'm actually checking this Ac-Dc converter idea to lower the weight of my kepco ate 75-8 psu, at 57 pounds its an heavy weight lollUsing an smps to replace the x-former, i need at least 100vdc at 8 amps $$$$ loll and put it before my pre-regulator section.I like the concept idea of variable ac phase controlled scr rectifiers psu's like the Kikusui Pad75-5 i have, it cut the weight and size in halfwhile almost keeping the same power output75-8 vs 75-5

author: Raj
author_rank: Frequent Contributor
timestamp: September 26, 2018, 04:10:44 pm
content: Quote from: coromonadalix on September 26, 2018, 02:57:34 pmHoly cow. This is why we have more smps now daysWhen I was taking my welding classes, dealing with traditional transformer welder was a huge deal. New ones weigh nothing