## A Simple but Accurate Constant Current Source

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
evahle
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### A Simple but Accurate Constant Current Source

Well, it's been about 9 years since I posted in this forum. It's a long story.
Anyway, I've been working in my new lab of my extra bedroom and decided to make a simple CCS.
I'm not sure what all I can upload but I'll try to upload the photos.
It's pretty accurate. Better than 1 %. You can choose anything from 1.2mA to 128mA in increments of 1mA. I'm already using this a lot. The only drawback is that I had to measure each resistor with a 4 1/2 digit multimeter to get the accuracy, and then parallel a few to get the right resistance.
This is a great circuit for testing LEDs at the current that I'll be using for many of my circuits. I've also tested the LUX output of many of my LEDs at specific LED currents chosen using this device.
Attachments
Schematic

evahle
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### Re: A Simple but Accurate Constant Current Source

I'll try to upload the spreadsheet in this reply.
Attachments
Spreadsheet showing all possible combinations of currents.

evahle
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### Re: A Simple but Accurate Constant Current Source

This circuit is great for testing Leds. Want to know what the Led voltage is at a certain current? Just connect the Led to the output, then select the current you want, and measure the voltage across it. That's simple.

This circuit can also measure low value resistors. Just connect the resistor to the output (at the ends of the resistor), then select 100mA, and measure the voltage across the resistor (connect the DMM close to the resistor body). R=10 x Volts. (Also known as the 4-wire method)

I needed a CCS circuit that I could use to select a current that had a wide range. I couldn't find anything on the internet or Ebay, at least nothing inexpensive. I like to design and build my own test instruments that I can't find or is too expensive. This circuit was one of them.

If you decide to build it, be sure to parallel the resistors to get as accurate as possible. It takes time, but well worth it.

Eugene.

(Those who ask the most questions, are the smartest people I know!)

haklesup
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### Re: A Simple but Accurate Constant Current Source

Have you checked the accuracy over a range of temperature? 1% is about as good as one could expect with resistors, its probably closer to 3% when you check it over a wide operating temp range but still very useful. Did you use precision resistors?

evahle
Posts: 182
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### Re: A Simple but Accurate Constant Current Source

No I didn't. Like I said in the post, I used resistors in my rather large collection and kept calculating the parallel equivalent, then measuring each one with a good DMM to get the exact resistance I needed. Since I will only be using it in the same lab at my home, I didn't have to worry about temp changes. Besides, keeping it simple and inexpensive was my primary goal along with being as accurate as possible. I'm sure others will find even more uses for it too. It seems like I'm always wanting some test instruments that I can't find or is just too expensive, since this is just a hobby now. You're welcome to improve on it though and post it back here.

evahle
Posts: 182
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### Re: A Simple but Accurate Constant Current Source

Wow, deactivated the photos in this post. Unless we can get this problem with photos fixed, I just can't see me adding any more projects. Sheez. Frustrating.

Janitor Tzap
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### Re: A Simple but Accurate Constant Current Source

evahle wrote:
Fri Jun 15, 2018 7:21 am
Wow, deactivated the photos in this post. Unless we can get this problem with photos fixed, I just can't see me adding any more projects. Sheez. Frustrating.
Hmmm............

evahle,

What are the names of the attached files?

I'm wondering if you did a Google Image Search for them, would they be viewable from Google?

If so......
Try copying the Image Location from the Google Image Search, and see if you could insert the Image into your post that way.

Signed: Janitor Tzap

evahle
Posts: 182
Joined: Mon Aug 13, 2007 3:48 am
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### Re: A Simple but Accurate Constant Current Source

I uploaded them directly from my computer. They also can be seen in an album in my Facebook profile. It's set to public so anyone who's a member of Facebook can see them. Just search for Eugene Vahle to find my profile.

Janitor Tzap
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Joined: Sat Aug 12, 2006 5:17 pm
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### Re: A Simple but Accurate Constant Current Source

Okay,
This has too do with Facebook.
{Has nothing to do with this website.}

I tried to look at your pictures, but was immediately stopped with a Log-in screen.

Go back into your Facebook profile and see if it has been modified.
With all the security holes the Facebook has.
I bet they are trying to plug them quickly as possible, without thinking it would be an issue with most of they're members.

As I said in the other posting.
What this Message Board needs is an "Art Gallery" that the members can upload Pictures, Diagrams, and Images too.
That way it makes it a lot easier to put images into postings.

Signed: Janitor Tzap

evahle
Posts: 182
Joined: Mon Aug 13, 2007 3:48 am
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### Re: A Simple but Accurate Constant Current Source

Actually I didn't upload to this website using Facebook. As I said, I uploaded to this website directly from my computer. Have you tried uploading any pictures? If so, let me know how that turns out.
If you decide to look at the photos through Facebook, You'll have to log in to their website first.

Janitor Tzap
Posts: 1311
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### Re: A Simple but Accurate Constant Current Source

evahle wrote:
Fri Jun 15, 2018 3:24 pm
Actually I didn't upload to this website using Facebook. As I said, I uploaded to this website directly from my computer. Have you tried uploading any pictures? If so, let me know how that turns out.
If you decide to look at the photos through Facebook, You'll have to log in to their website first.
WHAT???

Firstly.....
This Website has never had Photo/Image storage on it.

Second.
I tried to do a Image Paste of a JPG file into this post, which didn't work.

Third.
The only way you could copy an Image from your own computer too this site,
is because the OS {Operating System} is setup to act as a Server.

Look at your OS and see if your computer is setup as a Server, and if settings have changed because of a update.

I'm using Windows 7 Home 64-bit Version.
It doesn't have Server Networking built into it.

If your Computer isn't setup as a Network Server.
Then I don't know how you were able too upload images too this website in the first place,
It should not of been possible.

Signed: Janitor Tzap

CeaSaR
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Joined: Sat Nov 08, 2003 1:01 am
Location: Phoenixville, PA USA
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### Re: A Simple but Accurate Constant Current Source

Under the FAQ.
http://forum.nutsvolts.com/app.php/help/faq#f3r3
This goes for any attachment, which you can see further up the FAQ. IIRC, the reason this was never allowed was due to fear of losing space / space constraints for the Board. In this day and age, this shouldn't even be a consideration.

CeaSaR
Hey, what do I know?

evahle
Posts: 182
Joined: Mon Aug 13, 2007 3:48 am
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### Re: A Simple but Accurate Constant Current Source

I agree CeaSar. I mentioned earlier that I could store over 100,000 photos on a single flash drive. I have several. I've been in contact with Sean, the Administrator and so far he's been able to upgrade the forum some. My old photos though were deleted and I'm still not able to upload any photos or documents. I sent him a link to another forum that is similar to this one that allows photos with members' posts. I'd hoped to liven up this forum by making fun projects for the readers to enjoy, but isn't possible without pictures.

CeaSaR
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Joined: Sat Nov 08, 2003 1:01 am
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### Re: A Simple but Accurate Constant Current Source

I agree with that assessment. Ease of use and what is considered standard practices trumps any old concerns that may have been precedent over 10 years ago. In order to make this board attractive to the newer generation, image and file hosting is just a basic requirement.
CeaSaR
Hey, what do I know?

evahle
Posts: 182
Joined: Mon Aug 13, 2007 3:48 am
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### Re: A Simple but Accurate Constant Current Source

Alrighty then, the picture uploading has been fixed!! I'll try to upload the schematic for this project.
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