minict curve tracer, zener diodes, etc - Page 1
Forum section: electronics / projects

author: cncjerry
author_rank: Unknown
timestamp: November 08, 2016, 07:46:28 pm
content: I picked up the April 2015 QST and found an article written by Veikko, N7VK about a mini curve tracer and decided to build it. It took some learning as I haven't touched the 8051 in a while but with a little help from Veikko, I got it running. First, I am amazed that more people haven't built this curve tracer. Veikko wrote almost 6k lines of code on the PC application side and overall it works very well. I've been using it to explore various active components and plan to use it to check for leaky FETs in HP volt meters I am repairing.In playing around with it I found something that I've never noticed about zener diodes. First, they aren't that accurate, around 5%. Second, as you can see in the attached trace, the knee varied between zener voltages with the lower values having a smoother knee vs the higher values. I checked several packs of the cheap eBay specials and they track very closely.The trace on the left is for a 2.2V and the right, 6.8V. The little circle on the 6.8V trace shows the zener voltage at 7.004V and the 2.2V trace is actually 2.275. Both of these voltages compare closely to a test circuit I made.Is this typical?Thanks.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 08, 2016, 08:07:55 pm
content: The behavior of the zeners is normal. The low voltage one are not that good. At about 6-7 V they are usually best (sharpest knee) and get less good at higher voltages.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 08, 2016, 08:09:29 pm
content: I have a couple or 3 or wait a minute 4 curve tracers.Are you showing the forward and the reverse voltage?

author: cncjerry
author_rank: Unknown
timestamp: November 08, 2016, 09:05:56 pm
content: yes, forward and that little drop off the left of the curve is -.644V.I have two tracers, this one I just built and one of those cheap ones built on a transformer that attaches to the XY display on a scope. This one will do the AC sweep at 60hz (like the transformer type using the DAC on the 8051.

author: cncjerry
author_rank: Unknown
timestamp: November 08, 2016, 09:53:09 pm
content: The first attachment is another trace using a 9.1V zener and a negative starting voltage that shows the reverse voltage of -.777V and current of 6.122ma. You can see where the two plots overlap (reference in red, current in green and overlap in yellow).The minict Veikko designed is somewhat limited in current to less than 20ma and voltage of about 10V, maybe as high as 14V depending on where you calibrate it. You can always add higher voltage transistor amps as well as a voltage divider to the base circuit.The second file is a trace of a 2n3904 transistor. I haven't checked the accuracy off this sweep yet. I ran it using a script file Veikko supplied. That is one of the more interesting features of his code. You can generate a script file almost automatically and then edit it, etc.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 08, 2016, 09:57:36 pm
content: Ok,Two pics..First with curved knee is normal .633 diode drop at .2volts per divisionSecond is 22 V Zener at 10 volts per division and a little parallax error from iphone.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: November 08, 2016, 10:21:33 pm
content: Quote from: cncjerry on November 08, 2016, 07:46:28 pmYes.Voltages below about 5.7 V --> Zener effect.Voltages above about 5.7 V --> avalanche breakdown effect

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 08, 2016, 11:41:58 pm
content: Looks like a pretty interesting curve tracer.I will have to read the download.Yes your results seem about right.

author: edavid
author_rank: Super Contributor
timestamp: November 08, 2016, 11:59:07 pm
content: Here's the article:http://www.arrl.org/files/file/QST%20Binaries/Apr2015/Expanded%20Text.pdf

author: kermitfrog
author_rank: Contributor
timestamp: February 23, 2018, 02:06:53 am
content: I read the QST article and had considered building one, but couldn't find any indication on where to get the software. Is it still availble on the ARRL site? Do you have a link?

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 23, 2018, 02:14:08 am
content: Love the 575. I am always thinking I should get one...just because.

author: Johnny10
author_rank: Frequent Contributor
timestamp: February 23, 2018, 02:27:15 am
content: Get the 400V version.And you could probably build a tube curve tracer test jig for it also.That is going to be a project in the future.

author: danadak
author_rank: Super Contributor
timestamp: February 23, 2018, 11:03:18 am
content: kermitfrog, I looked author up in qrz.com call sign database, FCCshows his address as -KANTO, VEIKKO A3355 W Lobo RdTUCSON, AZ 85742If you can get it please post it on this thread.Regards, Dana.

author: RolandK
author_rank: Regular Contributor
timestamp: September 12, 2019, 07:00:57 am
content: The complete description of the minict can be found in this thread:https://www.eevblog.com/forum/projects/curve-tracer-designs/msg2139304/#msg2139304

author: mikerj
author_rank: Super Contributor
timestamp: September 12, 2019, 11:38:25 am
content: The (minimal) homepage for the project seems to have moved tohttp://kc4zvw.shell.freeshells.org/project5.html