OFF-LINE. ESR Meter

This small electronic project is related to the post of capacitors and computers (http://boscohurtado.blogspot.com.es/2012/10/off-line-condensadores-y-ordenadores.html), and it is my contribution to the construction of such devices have find in the internet, whose schemes have harnessed and adapted to this personal model. The design of the final circuit is the set below this text . In this case it was difficult to find the microampere ammeter panel , which recommended was 100 μA , but I could only locate the 50 μA panel, and it took over two months to get it . I had almost finished the project for that long time expecting only to place the panel. The frustrating thing is that many similar projects I wanted to do always has been that I could not locate a particular component , especially in the case of small integrated circuits , taking the rest by hand, which leaves you no choice to do nothing . This at least saw the light and was fine.

ESR Meter Schematic

(correction circuit sept 2014 )

 Outline and mounting components on the motherboard .

 Detail of transferred toner to the plate by means a waxed paper printed  from a laser printer. The paper used is the protective sheet of adhesive labels on A4 .
http://boscohurtado.blogspot.com.es/2012/11/off-line-circuitos-impresos_21.html 

 Motherboard almost finished, except installing the integrated circuits, the optocoupler between the main circuit and buzer and connecting cables to the battery, the LEDs, potentiometers and panel.

View of the connections between the motherboard and the top of the meter where the controls are.

Detail of an encapsulated home an optocoupler with a white LED and LDR photoresistor with a heat shrink. In normal operation the white LED is off and the LDR has a resistance of several megaohms , then there is no way to current. It is essential to seal well all together, the slightest input light activates the LDR . When turned on the red light error by short, white LED that is in parallel with it lights too, the LDR drops to few Ohms value and passes the current to the base of a transistor, which is what triggers the buzer . I didn’t found another more effective way to activate the buzer . I didn’t find any optocoupler in any of the electronic stores , months later I got a few of them from useless switching power supplies and other electronics.

Mounting the circuit in the box, failing to install the ammeter.

In case of not finding a 50μA ammeter is possible to adapt a similar one in range replacing the internal resistance by other potentiometer and calibrating it to give the needle width almost to the top of the scale measuring a new condenser 2200μf and 25v. 

See also:

http://boscohurtado.blogspot.com.es/2014/04/recalibrar-un-voltimetro.html

ESR Meter with cables to connect to the legs of the capacitor , with a copper tube 1.5 mm in diameter. I prepared two isolated terminals to insert them into the legs of the capacitor for an   easier reading. Do not need the polarity , because of  the alternating current supplied by the meter. Red and black colour doesn’t mean positive and negative, are not necessary in this case. It’s recomended short circuit with a resistor or a bulb the legs of the capacitors to discharge it before reading.
Do not use with industrial or higher capacitors.

Testing a condenser, it specifically showed good but that little swelling on the top cover will indicate that short-term problems and needs to be replaced. However, I keep these capacitors for the tests and experiments or for further research.

Another example with one of lower capacity and various readings capacitors.

Source:
http://kakopa.com/ESR_meter/schema02.htm
As I have seen that there are people interested in riding one , I let the scheme of mine if anyone wants to try it . The circuit could be simplified buying directly a piezo speaker buzer with that function. You can also modify the values ​​of the resistors and capacitors to change the 556 beeps every “x“ intervals ... if not it sounds like a car horn. This image it’s scanned at twice the normal size, scale must be set to print and fit the values ​​of the coordinates in milimeters.

Reference Chart measurements. With the needle almost at full scale would give the optimum value for a capacitor in good 2200μf up , in this case when the scale of the ammeter 50 μA have indicated that scale values ​​is 50 , does not indicate a value of resistance in ohms , it’s just a reference value. ESR value could be obtained by other means correspondence but in this type of meter was not the goal . Each capacitor even within the same capacity and different manufacturer can give a different value, even within the same range of a different nominal voltage capability gives different results , it is best to use this meter to compare with equivalent capacitors in good condition which are indicated in this table ( the indicated values ​​are also averaged between capacitor values ​​within undamaged various voltage ranges ) .