Electronic load, why only constants? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 28, 2018, 07:38:04 pm
content: I am searching for gear to bye and am wondering on why electronic loads only have constants like constant voltage, current and so on.Do none ever need to know how something react on suddenly change in current, i.e. a relay turning on a fan or a heater?Or what about voltage change?

author: Pinkus
author_rank: Frequent Contributor
timestamp: October 28, 2018, 08:04:46 pm
content: most do have a RS232 (often TTL) or an USB interface where you can program them to do what you want (e.g. jump from 10ma to 10A and back for 1000 times.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 28, 2018, 08:06:14 pm
content: Check this document:https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/8600_Series_manual.pdfPages 51-55 seem to answer your question.

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 28, 2018, 08:28:04 pm
content: Okay thanks, great news (for me) :-)I hope to spend less then 500$, do you have some recommendations for a decent lab?

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 28, 2018, 08:57:22 pm
content: BK Precision has an entry model for $545.http://www.bkprecision.com/products/dc-electronic-loads/8540-150-w-dc-electronic-load.htmlI recommend you check its specs and manual to see if that is what you need.By the way, the term "constant" is a bit misleading. This doesn't mean that things cannot vary. It only means that this is the parameter that you're going to control, regardless of the others. So, in constant current (CC) mode, your dummy load will maintain the programmed current no matter how the other parameters (voltage, resistance) react. The same is true for CV or CR. Some models even offer CP (constant power).

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 28, 2018, 09:57:47 pm
content: Okay great, that means, if I set the CC to 500mA and 5V but try to give it 7V and 200mA, it will just force the voltage down to keep the 500mA?I'll look at the BK, but what about the "less brand names" like Maynuo and so on?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 28, 2018, 11:14:45 pm
content: Just hook a MOSFET to a resistor and run it with a '555. Easy load step generator, with sub-1us switching times -- more than fast enough for testing control loops.Tim

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 28, 2018, 11:16:17 pm
content: Quote from: FriedMule on October 28, 2018, 09:57:47 pmIf you set CC to 500mA, no matter what voltage (within the specs) you apply to the load , it will try to draw 500mA.QuoteI'm not acquainted with other brands, unfortunately.

author: Rick Law
author_rank: Super Contributor
timestamp: October 29, 2018, 01:48:33 am
content: Quote from: bsfeechannel on October 28, 2018, 11:16:17 pmI agree with whatbsfeechannelsaid, but I want to add emphasis on the word try: "...it willtryto draw 500mA..."It served me well when I finally realized it really is a limit rather than a constant, it may serve you well also to remember while it is called constant current or constant voltage, it really is limit and not constant.The electronic load will keep on lowering it's throttle to allow more current through - as much as your 7v 200mA supply can give. As current increases, unless the 7v/20mA supply is voltage-regulated, the supply voltage may sag. It may succeed in giving out 500mA, or not. In the process, the voltage may sag - the more current, the more the voltage sags. How much current it can supply and how the voltage sags is entirely dependent on the design of the power supply.

author: ArthurDent
author_rank: Super Contributor
timestamp: October 29, 2018, 04:27:57 am
content: I bought a like new 3711A electronic load (see photo) that is sold under labels of Tekpower, Circuit Specialists, and Array, on eBay for about 1/2 price and it is really nice. Maximum ratings are up to 360 VDC, up to 30 A, and up to 300 watts. All the major current production electronic loads are really versatile, a lot with logging programs and computer control.There are also a large number of low end units and kits that can be purchased on eBay for very little money if you just want to try one and not spend a lot.

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 05:03:07 am
content: Great replies, I do want a decent model and I do think maybe +25V at +3A would be nice, I'll look at all of your suggestions.My knowledge about building electronic is to low for building my own reliable test gear.unfortunately do I not have much money either.Any more suggestions, also on what I shall look fore if I am using it for simulating DC loads below main voltage?

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 05:15:22 am
content: Quote from: bsfeechannel on October 28, 2018, 08:57:22 pmWhy would you ever buy BK precision when it's ITech (BK daughter company) sold at higher price? You could simply spend less or get higher end model at the same price. Also there is Maynuo.

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 05:20:57 am
content: So ITech is the same as BK?Yes there is Maynuo, Rigol and others but I do not know if they are okay or just "HangLow" models? :-)

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 05:23:15 am
content: Quote from: FriedMule on October 29, 2018, 05:20:57 amYes, I don't know if all models are exactly the same but most of them certainly is the same thing made at the same place. Maynuo is basically the same thing. It's not like there is a difference like between Rigol and Keysight. You'll hardly notice any difference, also there is only little price difference between Maynuo and ITech.

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 05:25:40 am
content: Quotehttp://www.bkprecision.com/about-us.html

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 05:42:31 am
content: The Rigol looks like it is advanced with all those buttons and the Maynuo looks like the BK or ITech.I know that we may be around 500-600$ but if 100$ more does it, then okay.I am lost in choosing:-)

author: DuPe
author_rank: Regular Contributor
timestamp: October 29, 2018, 07:06:14 am
content: there is already a thread for electronic load recommendation:https://www.eevblog.com/forum/testgear/digital-load-recommendations/msg1367450/#msg1367450orhttps://www.eevblog.com/forum/testgear/it8512(a)-or-the-m9812/msg934851/#msg934851

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 07:10:39 am
content: Okay great thanks, I'll look at that! :-)EDIT: It's look like it is only one commendation and a tiny review comment.Do anyone know the Rigol or more about other marks?

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 29, 2018, 07:20:59 am
content: Quote from: wraper on October 29, 2018, 05:15:22 amYou mean lower?Because in another thread I showed that the products of some "reputable" manufacturer is overpriced and I was burnt at the stake for that.

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 08:57:58 am
content: Quote from: bsfeechannel on October 29, 2018, 07:20:59 amI said that BK is ITech sold for more. English is my 3rd language but google translate agrees with what I wrote.

author: sstepane
author_rank: Regular Contributor
timestamp: October 29, 2018, 09:02:25 am
content: Hi,In this price range I would look at Applent AT8612. It's a pretty decent device.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 09:47:45 am
content: Quote from: FriedMule on October 28, 2018, 09:57:47 pmBoth Maynuo and Itech have a good reputation and the story is that those and BK's models are designed by the same person. The advantage of Itech is that the devices speak SCPI.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 09:50:04 am
content: Quote from: bsfeechannel on October 29, 2018, 07:20:59 amIf you're referring to the soldering iron thread, you got burnt because there wasn't any proof. We have extensive tests and teardowns of various electronic loads that show they're essentially the same thing.Please keep discussions to the relevant thread at hand.

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 10:03:34 am
content: Quote from: Mr. Scram on October 29, 2018, 09:47:45 amIt is told that Maynuo is designed by the people who left ITech but who knows how much truth is in it. But ITech is literally a subsidiary of BK. Why would you pay more for BK logo when you can buy it under brand which actually makes those DC loads instead of paying more to parent company.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 10:04:56 am
content: Quote from: wraper on October 29, 2018, 10:03:34 amThe question is whether it really is just the logo. Support and parts avaliability can be relevant too, though I have no reason to suspect that's better or worse either way.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 29, 2018, 02:25:34 pm
content: Quote from: wraper on October 29, 2018, 08:57:58 amMy dyslexia strikes again. I read "when Itech is sold at a higher price". Fortunately I got what you mean.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 29, 2018, 02:49:35 pm
content: Quote from: Mr. Scram on October 29, 2018, 09:50:04 amBut I deserved it. I'm a heretic. I confess. I dared to challenge the established dogma that, if a product is expensive, it is because some otherworldly technology is being employed and it would be a sacrilege to reveal that it is not to mere mortals.So I promise to abide by the holy doctrine and never commit this sin again.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 02:51:37 pm
content: Quote from: bsfeechannel on October 29, 2018, 02:49:35 pmAgain, keep discussions in the relevant thread.

author: bsfeechannel
author_rank: Super Contributor
timestamp: October 29, 2018, 03:04:14 pm
content: Quote from: Mr. Scram on October 29, 2018, 02:51:37 pmBut it IS relevant in this thread. I've been questioned why BK Precision when you can get the same s for a lower price. I won't make the same mistake again.

author: glarsson
author_rank: Frequent Contributor
timestamp: October 29, 2018, 03:12:53 pm
content: Note that iTech and BK are not the same. There are always differences, e.g. a nicer display (dot matrix) on the BK vs. cheaper display (starburst) on the iTech.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 03:18:49 pm
content: Quote from: bsfeechannel on October 29, 2018, 03:04:14 pmCan you show support is exactly the same for both brands? That's interesting information to have.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 03:19:56 pm
content: Quote from: glarsson on October 29, 2018, 03:12:53 pmiTech has dot matrix displays too, but those models tend to fetch higher prices as well.

author: glarsson
author_rank: Frequent Contributor
timestamp: October 29, 2018, 03:25:07 pm
content: Yes, but I meant models with similar specs. The BK model will be a little better and more expensive.Also, if consumers buy products then the product is not unreasonable priced.

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 03:53:55 pm
content: Quote from: glarsson on October 29, 2018, 03:25:07 pmReally? BK8500 series have segmented display and cost $1,155+http://www.bkprecision.com/products/dc-electronic-loads/8500-300-w-programmable-dc-electronic-load.html#galleryLargeModalThen you can buy ITech with the same display for more than twice less and even IT8500+ series with display having 2 rows it still would be much cheaper.

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 04:35:13 pm
content: I think that it can be a jungle, looks like it:-)But how much quality / price do I need?I am thinking of a load that after 5 years of normal use and learning, properly still is an okay tool in my lab.So nothing wild nor something sh*tty.As I understand you all, it is a choice between the BK-lookalikes and not i.e. a Rigol?

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 29, 2018, 04:42:02 pm
content: Quote from: FriedMule on October 29, 2018, 04:35:13 pmThe Rigol had quite a few issues when released and as far as I'm aware it hasn't improved a lot. Many people here seem to have been disappointed by it.

author: wraper
author_rank: Unknown
timestamp: October 29, 2018, 05:00:57 pm
content: Quote from: FriedMule on October 29, 2018, 04:35:13 pmWhichever you buy, BK, ITech or Maynuo, you should be fine. So choose whatever fits the spec and is the cheapest. If you order Maynuo of ITech from Chinese sellers you could save a lot additionally but unlikely to have a real warranty. In any case, none of those should fail unless you do something unreasonable to them.

author: FriedMule
author_rank: Frequent Contributor
timestamp: October 29, 2018, 06:41:16 pm
content: Thanks a lot to you all!Rigol is out and a cheap BK clone it is then:-)

author: glarsson
author_rank: Frequent Contributor
timestamp: October 29, 2018, 07:17:30 pm
content: When I bought my iTech the corresponding BK model used a dot matrix display. This nay have changed since then.