PIC based high-resolution cap meter

[mimoletti]

Hi,

I have changed all resistors. Now they are all 1%. The voltages are:

RA0 = 0,14V;
RA2 = 3,31V;
RA3 = 4,92V;
RB3 = 3,60V;

The comparator is not oscillating I have checked it with my oscilloscope.

 

[jjw]

Something is pulling RA0 down or it is floating.
Is RA0 connected to R5 and C2?
If connected, check any shorts from C2 to gnd.
If no shorts, C2 might be faulty.

 

[mimoletti]

I have checked again pcb and now it works. Thanks at all for your support.

 

[gophert]

I have checked again pcb and now it works. Thanks at all for your support.

I appreciate you checking to let us know it works but is there any reason it started working? Nobody will laugh at you if it was a dumb mistake - we'll just laugh at our old memories of the time we made the same (or similar) mistake.

 

[mimoletti]

I'm sorry, you're right. I made the PCB with my cnc in this way:

Perhaps there was a bit of Copper between two tracks.

Regards Massimo.

 

[周栩乐]

Hello!I'm new here.I'm from China.I'm interested in this product and want a PCB for this product.Can you offer me the PCB picture?

Thank you.

 

[Ian Rogers]

Hello!I'm new here.I'm from China.I'm interested in this product and want a PCB for this product.Can you offer me the PCB picture?

Thank you.

Still on Roman Blacks web site.. https://www.romanblack.com/onesec/CapMeter.htm

It was originally strip board.

 

[周栩乐]

Still on Roman Blacks web site.. https://www.romanblack.com/onesec/CapMeter.htm

It was originally strip board.

Thank you very much,but I still can't find where the PCB picture is on the website.Can you help me?Thanks.

 

[gophert]

Thank you very much,but I still can't find where the PCB picture is on the website.Can you help me?Thanks.

If someone helps you, you'll need to also help yourself. Read the link on the Roman black.com site and you will see...

"As the circuit is VERY simple (it's just a PIC and a few parts) I made it on veroboard (stripboard). It is really not worth etching a PCB for this project! A small SMD 5v regulator is soldered to the bottom of the PCB, all the other parts can be seen below; "

So, no, there is no PCB and no need for a PCB if you are making fewer than 5 pieces. If you are making more, it is a very easy board - you could draw it with a felt tip pen.

 

[Ian Rogers]

It was originally strip board.

You must have missed this bit.... The PCB's on this thread were done by someone else... Contact them

 

[周栩乐]

OK.I know.Thanks a lot!

 

[周栩乐]

I want to know whether it uses pic16f628 or pic16f628a?In China,there's only pic16f628a and it is difficult for me to buy a pic16f628 in China.Can it be replaced by pic16f628a?
Thanks.

 

[gophert]

I want to know whether it uses pic16f628 or pic16f628a?In China,there's only pic16f628a and it is difficult for me to buy a pic16f628 in China.Can it be replaced by pic16f628a?
Thanks.

The project was designed around the 628 - a part that doesn not have an internal oscillator. Roman Black claims either can be used with his hex code. It should work for either '628 or '628A but you will need to rely on an external oscillator since the configuration bits in the hex code are not set for internal oscillator (and 16MHz is needed for Romans design).

Also, here is a long discussion of the project on this site - including a PCB.

PIC based high-resolution cap meter

Hi, I have done a PIC 16F628 based pico-capacitance meter. I know there are a lot of other designs around but this one is very quick to build as it just uses one IC, the PIC (as it uses the PICs internal comparator as the oscillator). It measures down to 0pF and reads in 0.01pF resolution in...

www.electro-tech-online.com

 

[JimB]

Also, here is a long discussion of the project on this site - including a PCB.

PIC based high-resolution cap meter

Hi, I have done a PIC 16F628 based pico-capacitance meter. I know there are a lot of other designs around but this one is very quick to build as it just uses one IC, the PIC (as it uses the PICs internal comparator as the oscillator). It measures down to 0pF and reads in 0.01pF resolution in...

www.electro-tech-online.com

Gophert, you are a star!

You have just posted a link to the start of this thread.

JimB

 

[gophert]

That's the funny thing, the pcb that was so dire, is in the first few posts.

 

[JimB]

That's the funny thing, the pcb that was so dire, is in the first few posts.

OK, got it!

Not so much RTFM as RTWFT.

JimB

 

[周栩乐]

The project was designed around the 628 - a part that doesn not have an internal oscillator. Roman Black claims either can be used with his hex code. It should work for either '628 or '628A but you will need to rely on an external oscillator since the configuration bits in the hex code are not set for internal oscillator (and 16MHz is needed for Romans design).

Also, here is a long discussion of the project on this site - including a PCB.

PIC based high-resolution cap meter

Hi, I have done a PIC 16F628 based pico-capacitance meter. I know there are a lot of other designs around but this one is very quick to build as it just uses one IC, the PIC (as it uses the PICs internal comparator as the oscillator). It measures down to 0pF and reads in 0.01pF resolution in...

www.electro-tech-online.com

I know.Thank you very much!

 

[周栩乐]

I have another question.Why does the circuit given by the official website seem simpler than the component list given by the website selling kits?The list is blow:

1x Wire Black+Red for testing leads1x Manufactured high quality PCB 81 x 47 mm
1x LCD 16x2 HD44780 compatible
1x Trimmer Potentiometer 20K Side Adjust
1x Trimmer Potentiometer 500R 3362P
4x Resistor 1K5
1x Resistor 10K
1x Resistor 3K
1x Resistor 1R
3x Multilayer Ceramic Capacitor 100n 50V
2x Multilayer Ceramic Capacitor 22p 50V
1x Ceramic Capacitor NP0 270p 50V
1x Electrolytic Capacitor 470uF 16V
1x Electrolytic Capacitor 100uF 10V
1x PIC16F628A programmed with hex
1x LM7805 5V Voltage Regulator
1x 16.0000 MHz Crystal
1x DIP Socket 18 Pin
1x LED 3mm Red/Yellow/Green
1x 16 Pin Female Header
1x 16 Pin Male Header
1x Tact Switch Push Button 6x6 mm
1x Slide Switch On/Off
1x Terminal Block PCB Mount 2 position 5 mm
2x M2.5 Standoffs
4x M2.5 Screws
1x 9V Battery Clip
2x Crocodile Clips
1x 1N4004 Diode
1x Wire Black+Red for testing leads


But there aren't so many components in the offical circuit.Which circuit should I look at?Thanks a lot.
Also,there are two Trimmer Potentiometers in the list but there are only one in the offical circuit and they have different models.Are they different versions?Thanks.

 

[picbits]

Which website selling kits ?

 

[周栩乐]

Which website selling kits ?

High Resolution Capacitance Meter DIY Kit (Advanced Edition) with LCD | RH Electronics

Second Edition of Roman Black High Resolution Capacitance Meter. Required solder skill for assembling and testing. Now it has new PCB design, On/Off power switch, trimmer for calibration and easy LCD installation. The kit include LCD that can operate without backlight to improve battery life...

rhelectronics.net