Author Topic: Electronic load, why only constants?  (Read 5563 times)

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Offline FriedMuleTopic starter

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Electronic load, why only constants?
« on: October 28, 2018, 07:38:04 pm »
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?
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Offline Pinkus

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Re: Electronic load, why only constants?
« Reply #1 on: October 28, 2018, 08:04:46 pm »
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.
 

Offline bsfeechannel

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Re: Electronic load, why only constants?
« Reply #2 on: October 28, 2018, 08:06:14 pm »
Check this document:

https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/8600_Series_manual.pdf

Pages 51-55 seem to answer your question.
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #3 on: October 28, 2018, 08:28:04 pm »
Okay thanks, great news (for me) :-)

I hope to spend less then 500$, do you have some recommendations for a decent lab?
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Offline bsfeechannel

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Re: Electronic load, why only constants?
« Reply #4 on: October 28, 2018, 08:57:22 pm »
BK Precision has an entry model for $545.

http://www.bkprecision.com/products/dc-electronic-loads/8540-150-w-dc-electronic-load.html

I 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).
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #5 on: October 28, 2018, 09:57:47 pm »
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?
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Offline T3sl4co1l

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Re: Electronic load, why only constants?
« Reply #6 on: October 28, 2018, 11:14:45 pm »
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
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Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline bsfeechannel

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Re: Electronic load, why only constants?
« Reply #7 on: October 28, 2018, 11:16:17 pm »
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?

If you set CC to 500mA, no matter what voltage (within the specs) you apply to the load , it will try to draw 500mA.

Quote
I'll look at the BK, but what about the "less brand names" like Maynuo and so on?

I'm not acquainted with other brands, unfortunately.
 

Offline Rick Law

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Re: Electronic load, why only constants?
« Reply #8 on: October 29, 2018, 01:48:33 am »
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?

If you set CC to 500mA, no matter what voltage (within the specs) you apply to the load , it will try to draw 500mA.

Quote
I'll look at the BK, but what about the "less brand names" like Maynuo and so on?

I'm not acquainted with other brands, unfortunately.

I agree with what bsfeechannel said, but I want to add emphasis on the word try: "...it will try to 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.
 

Offline ArthurDent

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Re: Electronic load, why only constants?
« Reply #9 on: October 29, 2018, 04:27:57 am »
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.
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #10 on: October 29, 2018, 05:03:07 am »
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?
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Online wraper

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Re: Electronic load, why only constants?
« Reply #11 on: October 29, 2018, 05:15:22 am »
BK Precision has an entry model for $545.

http://www.bkprecision.com/products/dc-electronic-loads/8540-150-w-dc-electronic-load.html

I 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).
Why 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.
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #12 on: October 29, 2018, 05:20:57 am »
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? :-)
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Online wraper

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Re: Electronic load, why only constants?
« Reply #13 on: October 29, 2018, 05:23:15 am »
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? :-)
Yes, 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.
« Last Edit: October 29, 2018, 05:32:35 am by wraper »
 

Online wraper

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Re: Electronic load, why only constants?
« Reply #14 on: October 29, 2018, 05:25:40 am »
Quote
Asia - B+K Precision Taiwan, Inc., ITECH and Lodestar
Engineers in Asia know us through our ITECH, Lodestar and now our B+K Precision Taiwan brands. Offices in Nanjing and Taipei provide distribution and service throughout Asia, as well as the Middle East and Africa.
http://www.bkprecision.com/about-us.html
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #15 on: October 29, 2018, 05:42:31 am »
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:-)
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Offline DuPe

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« Last Edit: October 29, 2018, 07:12:10 am by DuPe »
 

Offline FriedMuleTopic starter

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Re: Electronic load, why only constants?
« Reply #17 on: October 29, 2018, 07:10:39 am »
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?
« Last Edit: October 29, 2018, 07:14:44 am by FriedMule »
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Offline bsfeechannel

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Re: Electronic load, why only constants?
« Reply #18 on: October 29, 2018, 07:20:59 am »
Why would you ever buy BK precision when it's ITech (BK daughter company) sold at higher price?

You 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.
« Last Edit: October 29, 2018, 07:25:52 am by bsfeechannel »
 

Online wraper

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Re: Electronic load, why only constants?
« Reply #19 on: October 29, 2018, 08:57:58 am »
Why would you ever buy BK precision when it's ITech (BK daughter company) sold at higher price?

You 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.
I said that BK is ITech sold for more. English is my 3rd language but google translate agrees with what I wrote.
 

Offline sstepane

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Re: Electronic load, why only constants?
« Reply #20 on: October 29, 2018, 09:02:25 am »
Hi,

In this price range I would look at Applent AT8612. It's a pretty decent device.
 

Offline Mr. Scram

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Re: Electronic load, why only constants?
« Reply #21 on: October 29, 2018, 09:47:45 am »
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?
Both 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.
 

Offline Mr. Scram

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Re: Electronic load, why only constants?
« Reply #22 on: October 29, 2018, 09:50:04 am »
You 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.
If 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.
 

Online wraper

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Re: Electronic load, why only constants?
« Reply #23 on: October 29, 2018, 10:03:34 am »
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?
Both 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.
It 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.
 

Offline Mr. Scram

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Re: Electronic load, why only constants?
« Reply #24 on: October 29, 2018, 10:04:56 am »
It is told that Maynuo is designed by the people who left ITech but who knows how much truth is in there. 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.
The 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.
 


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