5 Transistor ESR Meter Design

[Jay_Diddy_B]

have you this version in pdf as well,as it shows the track routing,cheers Paul m3vuv

See attached.

Regards,
Jay_Diddy_B

[m3vuv]

whats with c2 and r11?

[Jay_Diddy_B]

whats with c2 and r11?

I assume that you are asking about these parts in the LTspice model?




They represent the capacitor being tested.

DUT = device under test

TP1 and TP2 on the hardware schematic.

Regards,
Jay_Diddy_B

[m3vuv]

but the marking for c2 on the silkscreen is for a cap not the test points,it is on the artwork anyway,tp 1+2 are on the oposite side of the board,so what do i fit in the markings for c2 on my pcb?

[m3vuv]

also i dont see c9 or 10 on the schematic.but they are on the silkscreen.getting confusing!.

[m3vuv]

should c2 on the silkscreen not be c1? on the schematic??

[Jay_Diddy_B]

Hi M3VUV,

You missed this note on the drawing:




To make it easier for you have attached a pdf schematic with the changes for the 1mA meter movement. This is a hardware schematic and matches the board layout that I shared.

Regards,
Jay_Diddy_B

[m3vuv]

 jay,that makes sense now!,cheers Paul 73.

[roydc2010]

Hello Everyone,
I really like this meter and have been attempting to build one. I used a PCB layout from 5QESR.  Q2-Q5 are wrong on the silkscreen. The flat part of the transistors should be turned 180 degrees from what the silkscreen says. I put everything together and with the input terminals open circuit, the meter deflects to the right about 3/4 scale. It should stay to the right and deflect all the way left when shorted.

I saw J_Diddy_5 posted voltages and oscilloscope shots at various points in the circuit for troubleshooting so I measured these same locations. Here are my results:
Q3 Collector V = 2.52V
TP1 =                103mV pk-pk
Q3 Base V =       4.65V
Q4 Base V =       1.30V
Q4 Collector V = 2.64V
Q5 Base V =       1.30V
Q5 Collector V = 2.73V

For R24 the pot I am using a 50k ohm and it is set at the top of 50k ohm. Moving it lower makes the meter deflect further to the right with the test points open circuit. I see most people are using around 10-20k ohms.

I scoped the base of Q4 and Q5 and they are reading equal when inputs are open circuit.
D1 and D2 are UF4007
D3 and D4 are 1N5711
All caps are ceramic. C2 (oscillator cap) is 1.5nF +-5%. Should this be a tighter tolerance?

 

[Jay_Diddy_B]

Hello Everyone,
I really like this meter and have been attempting to build one. I used a PCB layout from 5QESR.  Q2-Q5 are wrong on the silkscreen.

Snip ...
 

Paul M6KUR used European Transistor when he designed his variation of the my circuit.

He used BC547 for the NPN transistors

and BC557 for the PNP transistors.

Both are in the same package, TO-92

The layout given by Paul in the 5QESR is correct for the BC547 and BC557 transistors.

The original layout is correct for the North American 2N3904 and 2N3906 transistors.





All the transistors, Q1 - Q5 should be 'wrong'.

Regards,
Jay_Diddy_B

[Jay_Diddy_B]

I put everything together and with the input terminals open circuit, the meter deflects to the right about 3/4 scale. It should stay to the right and deflect all the way left when shorted.

I saw J_Diddy_5 posted voltages and oscilloscope shots at various points in the circuit for troubleshooting so I measured these same locations. Here are my results:
Q3 Collector V = 2.52V
TP1 =                103mV pk-pk
Q3 Base V =       4.65V
Q4 Base V =       1.30V
Q4 Collector V = 2.64V
Q5 Base V =       1.30V
Q5 Collector V = 2.73V

For R24 the pot I am using a 50k ohm and it is set at the top of 50k ohm. Moving it lower makes the meter deflect further to the right with the test points open circuit. I see most people are using around 10-20k ohms.

I scoped the base of Q4 and Q5 and they are reading equal when inputs are open circuit.
D1 and D2 are UF4007
D3 and D4 are 1N5711
All caps are ceramic. C2 (oscillator cap) is 1.5nF +-5%. Should this be a tighter tolerance?

 

The component selection is okay.
5% tolerance on the capacitor is okay.

The DC voltages are all okay. This means the transistors Q4 and Q5 are biased correctly.

The meter reading is impacted by the shorting TP1 to TP2. This means C3 and C7 are there.

Check

R11, R12, C8

R20 and C6

If you have a scope look at Q5 collector voltage.

Regards,
Jay_Diddy_B

[roydc2010]

Thanks J_Diddy_B,

I didn't realize the emitter and collector were switched between the BC547 and the 2N3904. Still the layout of Q1 for a 2N3904 I thought was correct.
Collector connects to the high/+ and emitter connects to the low/- correct? Here is a picture of my board. I'm using 2N3904 (Q1,Q2,Q4,Q5) and 2N3906 (Q3).

I verified the resistors and caps you suggested and scoped Q5 collector:
R11 = 1.46k
R12 = 29.9
R20 = 32.7
C6 =   2.3 microF
C8 =   21.8nF
Q5 Collector = 3.04 V pk-pk

Thanks,
Dave

[Jay_Diddy_B]

Hi,

There is a mistake in the layout shared by Paul.

The negative side of the meter is connected to ground in his layout.

It should be connected to Anode of D4

5QESR Schematic - This is correct




5QESR Board - wrong



The negative end of the meter is connected to ground.

Disconnect from ground and connect to D4 Anode.


Let us know if this helps.

Is EasyEDA that bad, that allows the netlist of the board not match the schematic? Most half decent CAD systems won't allow this.

Regards,
Jay_Diddy_B

[roydc2010]

You were correct. I attached the negative side of the meter to the anode of D4 and it works great. It was my first time using EasyEDA. I just used the files 5QESR had available. A nice learning experience for me. Thanks for your help.

[m3vuv]

Hi all,ive just built the version of this using the 1ma meter movement,strange thing is with the test probes open it reads 3/4 scale to the right,when the test probes are shorted it goes fully to the left,any ideas?,cheers in advance.m3vuv.

[Jay_Diddy_B]

Hi,

It sounds like one of the two amplifiers  on each side of the meter is working properly.

Follow the procedure that starts here:

https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/200/

Start by looking at the DC voltages in the circuit. The voltages for the 1mA circuit should similar.

Then check the capacitors.


Jay_Diddy_B

[m3vuv]

well the voltages measure the following left to right (output from 7805=4,25),q2 collector=3.8v,q3 collector=2.08v,q4 base =1.02v,q4 collector= 3.03v,q5 collector=2.64v,q5 base=3,3v,all the caps seem ok apart from c2 thats 1.8nf,hope this helps,cheers m3vuv.

[Jay_Diddy_B]

Hi M3VUV,

Check the resistor in the emitter of Q5, R19. It should be 68

Why is the output of the 7805 only 4.25V? it should be 5V.

What is the input to the 7805?

Is the 7805 getting warm?

Regards,
Jay_Diddy_B

[m3vuv]

the input to the 7805 is 12v from a iinear psu,the reg is from china so suspect a reject/fake.

[m3vuv]

r19 is bang on 68 ohm.

[Jay_Diddy_B]

Hi,
Check or replace Q5.

Check R21 and R22.

The voltage on Q5 base should be 1.3V



The DC voltages in the Q4 and Q5 circuits should be the same. They are very similar circuits.


Jay_Diddy_B

[m3vuv]

well somehow i had a 30 ohm in place of r21,ive fitted a 27k,it seems to work but i can only get about %50 meter deflection with the probes shorted,thats also with r24 shorted also,any idears,its like the meter needs more drive,cheers m3vuv.

[m3vuv]

would lowering the value of r15 and r19 give me more meter drive?,the 7805 runs cool,what if i used a 8volt reg would that help and run it from 2x pp3 ie 18v?

[m3vuv]

Well,ive sorted it,i lfted the ground of the regulator and added an led + a 1n5711 schottky diode between that and ground(shall use the led as an on indicator later)that lifted the 7805 output to about 7.1v,now the meter will go full scale,and i get 125 milivolt at the test probes so still good for in circuit testing,im running it from a 3s 3p lion 18650 battery pack thats 7.2 ah so should last a while on a charge,will upload some pics soon,it reads about %10 low but thats as near as dam it for me!,cheers jay 73 m3vuv.

[m3vuv]

a few pics