Bench power supply questions - Page 1
Forum section: electronics / beginners

author: adras
author_rank: Regular Contributor
timestamp: October 09, 2017, 04:07:28 pm
content: Hey,I'm currently looking for a bench power supply. One thing I would like to play around with is mosfets controlled by an arduino. So I'm looking for a dual channel supply. And since I want to play with Mosfets I also need 10+ Amps. I'm basically looking for something versatile, so 60Volts, 15 Ampere maximum.But it seems like that doesn't really exist, or I'm too stupid to find something on Ebay (used or new). And these things get ridiculously expensive quickly.So my main question is: Why is it so hard/expensive to build a 60V 15A (900W) variable power supply?Besides that, there are a lot cheap power supplies for around 80USD which are capable of providing 30V 5A. I expect a dual supply to be twice as expensive but I'm really having trouble to find one of those.Am I expecting too much? Another thing I would to play with is creating an ESC for a quadrocopter motor using an Arduino and some other parts, which means I need a current of around 20-40Amps.EditIt seems like my best bet is to use two DPS5015(33USD) along with a switching mode Power supply 25A, 48V (70USD). That would cost me 136USD for a dual channel, 48V 12.5A/channel power supply. I'd rather prefer a finished box which I can just put on my bench, instead of putting it together on my own.

author: nanofrog
author_rank: Super Contributor
timestamp: October 09, 2017, 04:30:17 pm
content: 60V @ 15A per channel seems overkill for Arduino driven MOSFETs IMHO. They do exist, but they're not all that common (i.e. expensive).I suspect a more common 30V @3A (* 2 channels, trackable) would be enough. That way, you can series them to 60V or parallel them to 6A (2* 3A) or 10A (2* 5A), depending on the particular model.FWIW, I'm partial to triple output supplies as you get a better value (I'd suggest a used linear type/s). Particularly due to the typical instance where you need n + 1 PSU's, and you've only n at best.

author: adras
author_rank: Regular Contributor
timestamp: October 10, 2017, 08:11:14 am
content: And what about my other questions?

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: October 10, 2017, 09:12:07 am
content: Regarding your other question , why do you want to build ESC , when it's that easier to just buy one. Sure you can build one relativley easy but it's going to be more expensive. As far as amps go , that 20-40 amps refers to impuls current. Basically it works like PWM controller. Not that hard to build but aganin a lot more expensive then just buying a dedicated unit.Here is some information on it:https://en.wikipedia.org/wiki/Electronic_speed_control&&https://en.wikipedia.org/wiki/Pulse-width_modulationAs far as your power supply question , since you are from Germany may I recommend Batronix :http://www.batronix.com/shop/index.html

author: adras
author_rank: Regular Contributor
timestamp: October 10, 2017, 10:07:36 am
content: I think PWM is one of the fundamental things in electronics. And I want to implement it to get some practice. Nowadays one can download the arduino source code for PWM. But I think one should have done things like that at least once.Also I really like to play with some high current applications like motors, powerful LEDs or Peltier Elements. Batronix has the Siglent SPD3303C. I would buy it right away since it's a Siglent and it has three channels, but unfortunatelly I can get at most 9 Amps out of it. 6Amps if I use one channel to power an Arduino at the same time. Another example why I'm looking for Amps are flashlights, I would like to design a driver circuit for 4 Cree LEDs, each one of those already takes 3 Amps. Is it really that uncommon that I'm looking for such a versatile device?

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: October 10, 2017, 11:32:19 am
content: Try this:https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xagilent+system+power+supply.TRS0&_nkw=agilent+system+power+supply&_sacat=0Your problem is that you need high current , and high current = a lot of $$$$$$$

author: xani
author_rank: Frequent Contributor
timestamp: October 10, 2017, 11:40:49 am
content: Quote from: adras on October 10, 2017, 10:07:36 amThe problem is combination of high current, high voltage, and "lab supply" features like fully regulated voltage and current limit. This makes it harder from design point of view, use more expensive parts and on top of that, way less popular and thus you do not hit economies of scale with more typical power supplies. You can find 10-20 A supplies with decent pricing (like thishttp://www.circuitspecialists.eu/switch-mode-dc-bench-power-supply-adjustable-0-30v-0-20a-csi-3020sw/) but not with 60V (altho you can just buy 2 and parallelize them)as for ESCs you can just... test one without any load attached and then once it is working connect it to actual battery to get the current you need

author: adras
author_rank: Regular Contributor
timestamp: October 10, 2017, 12:22:11 pm
content: Thank you guys! Especially for the product suggestions.It seems like I have to accept that there is no cheap "Eierlegendewollmilchsau" (Yes, this German word exists and means: A pig that has wool, lays eggs and produces milk / All purpose animal).I'd still like to see other products. In this area I really have trouble to find something useful. So please post other products you have in mind.

author: james_s
author_rank: Super Contributor
timestamp: October 17, 2017, 07:48:58 pm
content: In general it's better to have multiple power supplies tailored to particular things rather than one massive one that tries to be everything. It's only a matter of time before you connect an Arduino or something and forget that you've got the thing set to 50V at maximum current. Power supplies are one of those things that you'll have several of sooner or later.

author: RD Tech
author_rank: Regular Contributor
timestamp: November 11, 2017, 09:39:16 am
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: Simon
author_rank: Unknown
timestamp: November 11, 2017, 12:18:25 pm
content: Quote from: RD Tech on November 11, 2017, 09:39:16 amI'm sorry but you don't do that, you have already had loads of free advertising from Dave's videos, if you are going to follow this form of promotion you will get banned and not earn yourself a good reputation. Behavior like this is usually attributed to scammers.

author: RD Tech
author_rank: Regular Contributor
timestamp: November 11, 2017, 01:30:12 pm
content: Quote from: Simon on November 11, 2017, 12:18:25 pmsorry

author: Simon
author_rank: Unknown
timestamp: November 11, 2017, 01:36:20 pm
content: Quote from: james_s on October 17, 2017, 07:48:58 pmQuite, technically one supply can't do everything (unless very very expensive). I managed to blow up an LED despite setting a current limit to 10mA, this was because i was using a 60V 50A supply that merely has a resolution of 10mA. I suspect that the current limit is before the output capacitor that can store enough energy to blow an LED even with a 10mA feed in limit.for this very purpose I did buy one of the RD tech units (yet to be tested) as from what Dave showed they will limit to a low current being inherently lower power units than my 1.2KW power supply not really made to regulate down to 22mW.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: November 11, 2017, 01:53:58 pm
content: Greetings. I bought the MingHe BST900, which is a small 900W SMPS. I used an old inverter tranformer and a bridge rectifier to drive the input and have been very happy with it. You can mod the display board to suit your needs. The Post Apocalyptic Inventor on youTube has a couple videos showing how he used an old Sony Amp as the mainframe for his SMPS units and gave me the idea. I am going to upload some videos for my build on my channel as well, The Combat Engineer. If you choose to use the BST900 (~$20) on eBay just remember it’s boost only.

author: oldway
author_rank: Super Contributor
timestamp: November 11, 2017, 01:58:19 pm
content: Fot high power applications, why not to make a simple unregulated power supply 0/60V 15 of more amps with a variac, a low voltage isolating transformer, a circuit breaker, a bridge rectifier with cooler and a big electrolytic capacitor.You could have 3 circuit breakers in = of 2A, 6A and 16A and choose to switch on the circuit breaker adapted to the protection you want.You could add a digital voltmeter and current meter.Always start with variac at 0V, so you never has to worry with surge current.Second hand variac is cheap (about 30€), low voltage transformer and electrolytic capacitors can be found for free in scrapped audio amplifiers...so it can be very cheap.

author: Simon
author_rank: Unknown
timestamp: November 11, 2017, 02:04:20 pm
content: Quote from: nanofrog on October 09, 2017, 04:30:17 pmThe cheapest in the UK is the QPX1200S if you add a "P" to the end of that you get the digital interface for another £150. anything less is a piece of junk like a digimess but they are OK if you want a rough and ready supply.

author: RD Tech
author_rank: Regular Contributor
timestamp: November 11, 2017, 04:20:13 pm
content: now you get one ?

author: Simon
author_rank: Unknown
timestamp: November 11, 2017, 04:23:23 pm
content: Now who get what? I have a QPX1200S, I also bought one of your 3-50V 5A modules so that I can control lower power levels because if you set the QPX1200S to 10mA and power an LED you will still blow it up.

author: RD Tech
author_rank: Regular Contributor
timestamp: November 11, 2017, 04:24:43 pm
content: did you use our power supply to try, if you use a small current , you can use dps3003, and set CC mode to try

author: Simon
author_rank: Unknown
timestamp: November 11, 2017, 04:27:18 pm
content: I have not tried your yet but it is one of the low power ones with 1mA resolution if i remember correctly. The problem can be when you have a current limited supply feeding the output capacitor that is usually the last component before the output switch and then when the switch is turned on you get all of the energy in the output capacitor dumped before the current regulation can help.

author: RD Tech
author_rank: Regular Contributor
timestamp: November 13, 2017, 06:51:13 am
content: Hi friendI am so sorry for long time replyabout your question, if you use our product, you must connect the LED first and set the value you need, then you open output, LED will not be burnt, the sequence is very important

author: Cliff Matthews
author_rank: Unknown
timestamp: November 15, 2017, 01:21:50 am
content: Quote from: RD Tech on November 13, 2017, 06:51:13 amI was impressed by Dave's examination of the products.. but I doubt a "sequence" is normal on good mainstream PSU's.Gee, I was getting vibes that Dave's next installment of "Setup and Electronics Lab for $x dollars" might include some suggestion for products like the DPS3003.Maybe if it's not too much to ask for another firmware menu item? (eg: "ramp-up delay=T").Simon, we mourn the loss of all perfectly good LED's.

author: splitzzzzz
author_rank: Contributor
timestamp: November 15, 2017, 01:56:19 am
content: $399 Altronicshttp://www.altronics.com.au/p/m8310-powertran-30v-20a-regulated-bench-top-power-supply/I have the 0-30V 5A version below. Cheap but works fine.http://www.altronics.com.au/p/m8305-powertran-30v-5a-regulated-bench-top-power-supply/

author: RD Tech
author_rank: Regular Contributor
timestamp: November 15, 2017, 06:05:53 am
content: thank you for your answer , my friendthis is my products, I need to tell the truth about our products ..about the Dave video , it is good , I like it too , hope you like our products