E.S.R. Meter (designed by Alan Wolke W2AEW)

This page documents my build of Alan Wolke's Equivalent Series Resistance meter.

The YouTube video for this can be found here.

If you're interested in hobby electronics, subscribe to Alan's YouTube channel here. Rarely do you find someone so knowledgeable who can put across the information in such a clear and easy to understand way. Top bloke!

I decided to re-draw the schematic from the video as it was difficult to build on a breadboard whilst pausing and rewinding the YouTube video.

I'll put a copy of the schematic up here soon - currently the pin numbers are wrong, so it is very confusing. below is a photo of the schematic I annotated whilst building and testing the circuit.

Below are a few shots of the breadboarded ESR meter running with a scope connected to the oscillator output and the restored DC output.

Oscillator period is about 7nS, giving a frequency of around 143KHz

The shot below shows a 10 Ohm resistor across the D.U.T. terminals and the panel meter deflects about 2/3 the way across. my panel meter was 500mA FSD, so I had to tweak the resistance values to provide more current to drive the meter.

The shot below shows a 'good' capacitor. the need barely moves from the 'zero' position.

My scribblings on the schematic note that the 10 Ohm resistance to ground acts as a voltage divider to turn the 5V oscillating output from the 4049 into a 200mV output. this is to prevent any silicon components (diodes/BJTs/ICs) 'turning on' when testing in-circuit.

The scope view below is for a 'bad' cap (I used a 10 Ohm resistor as I don't have any bad caps to test it with :( )

The scope view below is for a good cap (I have plenty of those)

This is a zoomed in view of one cycle of the 4049 output at 143KHz. notice the ringing at the start/end of the timing capacitor charge... presumably this is resonance of the timing components or the 4049 internals...?

The circuit transferred to stripboard. I used jumper pins to connect battery, DUT, zeroing pot & panel meter. I have plenty of Futaba/JR RC extension leads lying around, so I cannibalised a few to make 2-pin plug leads.

Plugged into the front panel for testing. 

A view of my manky soldering. spot the over-enthusiastic spot-cutting in the lower left corner - straight through the board!

The board was an interference fit in the box. Here's a top tip - buy the box to fit the stripboard after you've completed soldering. I bought the box first and had a bit of a mare fitting the components onto a piece of stripboard 2.2" x 3.5"...

The meter powered up, ready to go. 

Interestingly, my bench supply indicated the whole circuit used about 10mA @9V. 

However, when I added a 3mm green LED and a current limiting resistor across the battery/switch, the consumption went up to over 30mA, cutting the battery life to a third of what it could be.

To use, short the test leads and turn the dial until it's at 'zero' on the meter.

The shot below shows a good Cap. Needle on panel meter barely moves off 'zero'

A 10 Ohm resistor is shown below, emulating a bad Cap, as I don't currently have one.