5 Transistor ESR Meter Design

[Jay_Diddy_B]

Thank you for GIMP advice, it worked perfectly. See results in pictures 


Only problem I have is scale calibration, when I short test leads, pointer goes past 0, I understand I need to replace value of R22, 50K will work for this ?


Thank you Jay_Diddy_B for this awesome Project!!!

You should have a 10k pot in series with the meter. The pot is to zero the meter with the leads shorted together.

Here are a couple pictures of a completed ESR meter:





The zero pot is next to the meter.

Regards,

Jay_Diddy_B

[paronaram]

Thank you! 10k pot fixed my issue.
Was looking for some time on where to place my pot, and here is the best I came up with

[sarakisof]

Big ups to Jay_Diddy_B for the amazing job here. Has anyone verified if the Koogar's (R. Hirst) Eagle through hole 1.1 version works?

https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg407749/#msg407749

[sarakisof]

R.Hirst's pcb works fine. May i ask, can i use a 5K pot instead of a 10K one?
And then, R24 + Rmeter + 5K/2  = 7500 Ω (i'm using a 100uA meter).


The 10K  i have handy is a stereo one and doesnt fit (height) well into my enclosure. The mono that fits is a 5K one. Cannot source a mono 10K locally and don't want to wait and order for just one pot.

[labjr]

I would measure the resistance of the 10K pot when you zero the meter. Then try the 5K pot with a resistor in series where R=Measured Resistance-2.5K. Then you should be able to zero the meter when the pot is at about the center of rotation.

[sarakisof]

Finally found two salvaged 10K pots & built two meters. Haven't done meter scaling yet.

In one of them I'm running into an issue. While needle is at infinite all the way left normal position, by turning it on it moves up to the right.
By turning it off it returns back to its normal infinite position again. Shot & uploaded a 5 sec. video: https://we.tl/t-61vlIK32Ta

Any thoughts?

[sarakisof]

Finished with meter scale graph too. This one works fine.

Any thoughts about my second meter's issue, needle moving to the right a bit by turning the meter on, that i described above?

[paronaram]

Looks very nice! Good job! I like vintage embossed labels 

[diydidi]

Hi. Mine has the same problem. Slight deflection when powering on. @Jay_diddy_B do you think the transistors need to be matched perhaps?

[dio123]

I had the pcb produced by Jay_Diddy_B, and I ordered the components at lcsc, however I finished assembling everything and saw that it wasn't working.
After analyzing it, I saw that only the voltage next to Q3 - 2N3906 did not match, the others were ok.
Then I realized that the resistors r8 and r10, I bought in kilohms instead of ohms.
I can exchange the R8 for a 30R metal film resistor, but I can't find the r10 in any store in my area, the closest value I can get is 3.3 Ohms or 2.7 Ohms.

Any other solution, even changing resistors r7 and r9?

[p.larner]

i tried this design ages agomust of made 6x boards,if i remember one of the transitors was backwards,canr remember exactly as it was over 3yrs ago.

[p.larner]

I just dug mine out that i built maybe 5 or 6 years ago,it was working ok when last used,now on turn on the needle sits about a third of the way to the right with nothing connected,it does still seem to work tho,any ideas?.

[p.larner]

the arrl handbooks are for download on the piratebay with the tonne meter sw included,one old version i had from there let you do log scales but only for a max of 4 uses,just a case to reinstall the sw then and go againe.

[Anakiev]

Hi, everyone. Jay_Diddy_B thank you for sharing your work.

I am releasing my 5x7cm perfboard layout and an equivalent toner transfer version. This is the updated version witch includes the Jay_Diddy_B's lower shorted capacitor detector fix.
The frequency is about 92kHz. It draws 40mA with the LED on and 30mA with the LED off.

It was made with KiCad 7.0.9.


Some photos of the finished project.


There are two toner transfer versions. The original is identical to my perfboard. The noPSU is the same but you have to put the voltage regulator on a separate board.

[Jay_Diddy_B]

The LED will illuminate if the capacitor being tested is less than 25 .

Hello again! Don't get me wrong I like the project and it works fine except the two things below.

The short capacitor detector is not as expected. For me it triggers below 230ohms (not 25ohms) at full brightness (it starts turning on very dimly below 360ohms). It also adds DC offset (about 450mV). The short circuit current through TP5 and TP6 is 5mA. I've build partially another one (not the same design) and the LED starts turning on below 200ohms and below 160ohms is in full brightness. This one has 6.2mA current through TP5 and TP6. It adds 850mV DC offset.

Hi,

Try changing these three resistors:



This will lower the threshold for indicating a shorted capacitor to around 40 rising and 30 falling, there is 10 of hysteresis.

The original values are shown in brackets.

You have to run DC current through the test points in order to detect a resistor. To keep the circuit simple the Vbe of the transistor is used as a detector threshold. The maximum voltage on the test points is determined by the clamping diodes.


Jay_Diddy_B

[p.larner]

the pcb layout needs to bee black tracks on white for laser print and toner transfer blue on black looks nice but no good for laser printing!.

[Anakiev]

Hi, Jay_Diddy_B thank you for the update. I've made a new board with the new resistor values and it works much better now. For comparison the short detection now triggers (full brightness) bellow 56ohms instead of 230ohms before. The current through TP5 and TP6 dropped from 5mA to 3mA. The offset voltage also dropped from 450mV to 370mV.

I've added a jumper to the new board to be able to disconnect R14 which completely removes the voltage offset and the current through TP5 and TP6. Now I have both 5 and 7 transistor versions in one.

the pcb layout needs to bee black tracks on white for laser print and toner transfer blue on black looks nice but no good for laser printing!.

Two toner transfer versions were uploaded here.

[p.larner]

i made the 5 transistor version,the issue is,as soon as it it turned on the needle sits about a third from the left,any ideas whats wrong?,thanks. merry xmass all.

[Anakiev]

Compare the voltages with this picture. This may help you point witch part of the circuit is wrong.


You can find more information here. Check the whole thread it might be related to your problem.

[Elly D.]

Hi,

This is the ESR meter mention by BravoV:



Here is a very simplified and idealized model for the Silicon Chip ESR meter:




The test results from LTspice:



I have attached the model if people want to play with it.

Jay_Diddy_B

I'm currently redrawing this schematic in Kicad with different analog switches, a voltage regulator and selectable test frequency. I want to make this open hardware, yet it's not clear to me who's the original author and what this license is. Can BravoV and Jay_Diddy_B clear things up please?

[Jay_Diddy_B]

Elly D,

The schematic was published in Australian magazine called Silicon Chip in February 2005. I provided the LTspice model to illustrate how the circuit works.

There are more details in this link:

http://kripton2035.free.fr/analog%20esr/esr-lowohm-silic.html

Regards,
Jay_Diddy_B