Electronics > Projects, Designs, and Technical Stuff

Source Codes Archive of EPE Magazine

(1/2) > >>


I read many Everyday Practical Electronics (EPE) magazines.

I finished assembling a "PIC LCF Meter" project (February 2004), looked for a source code file to download, I clicked "Legacy Projects" (http://www.epemag.com/projects-legacy.html), then I clicked "Feb 2004" (http:/www.epemag.com/vault/0204.htm), it was said "Download area" (https://www.epemag.com/vault/downloads.html) that I clicked, and finally, I clicked "www.epemag.net/microcontroller-code.htm", and no ZIP file appeared.

I don't want to waste too much time searching until you find this.

Where do I download this file?

Thank you. Regards.

they seems to be here :

Thank, krypton2035

I read all the comments on Electro-Tech-Online.com writing that there were several bugs and they fixed their bugs.

It was a good idea, so I didn't know of these bugs.

I believed that this source code CAPMET790.ASM (version 4 or 5) belonged exactly to LCF Meter.

John Becker wrote:
Hi All,

These are the results of my findings when using different makes of 4011 in the LCF Meter when in Capacitance mode:

HEF4011BP  no problems
HCF4011BE  parasitic oscillation at about 6MHz
MC14011BCP parasitic oscillation at about 2MHz
RS4011B    parasitic oscillation at about 4MHz

Whilst a 4093 NAND Schmitt trigger can be used for capacitance measuring, the inductance mode cannot work with a Schmitt because of its hysteresis preventing oscillation occurring with LC feedback.

The parasitic oscillations were cured by putting a 68p cap between 4011 pin 5 and 0V (e.g. pin 7).

Further investigation showed that increasing the value of R4 from 1k to 2k helped with those 4011s prone to parasitic oscillation in cap mode. This reduces the initial surge current from 5mA to 2.5mA into/out of C7 at the moment of IC3b's logic change. This beneficial effect was especially noticeable with high values of external capacitor being measured. However, the use of 2k affects the capacitance calculation and so would require a modification to the program to compensate. Those of you with PIC programming facilities can experiment with this. The formula for R4 = 1k as the program stands for calculating C is

C = 1/(pi x 1 x F), where pi is calculated as 22/7

For R4 = 2k, the formula becomes:

C = 1/(pi x 2 x F), therefore pi can now be taken as 44/7

Consequently the cap calc statement at line 580 (line count taken through DOS Edit) currently saying "movlw 22" should be changed to "movlw 44".

It should be noted, though, that increasing R2 to 2K will roughly halve the maximum capacitance that can be measured before the software's time-out routine is triggered. It would also require (ideally) that R3 should be increased to 20k to maintain the 10:1 ratio between R3 and R4.

In conclusion, if your 4011 is giving problems, simply adding a capacitor of about 68p across R3 seems to be the simplest workable option (I would also have tried 47p had I had some free. I did try 10p, but that was insufficient). Another option is to purchase an HEF4011BP as I use without problems in my own unit.

This situation, as I've already said, is highly unexpected, having never experienced it before in the countless times I've used this type of circuit, but in which I guess I have probably always used the HEF device. I can only conclude that there is a degree of hysteresis built into the input of HEF 4011s which the other manufacturers don't include.

An intriguing situation. Thanks to you all for your input.

Another point - a certain Mike here on CZ commented that he had removed a statement from the previously advised revision (done to correct an erratic frequency readout at about 16kHz). He was right to do so (thanks Mike!) - it was a statement I'd forgotten to remove following the addition of a test routine when looking into the erratic problem. I have now deleted it and the amended code has been sent Alan, who will put it onto our site when he gets the chance!

Best wishes


But there is a difference of 2 RC formulas for π (pi) and 2.2:

fo = -----------   for LCF Meter
      π × R × C

fo = -------------   for Original Oscillator
      2.2 × R × C


I replaced 4011 by 74HC00 (better than 4011), I recorded the latest version and I tested correctly.



The Internet Archive saves billions of data all the time.

So there's an old EPE website, it's https://web.archive.org/web/20101230131002/http://homepages.nildram.co.uk/~starbug/epepic.htm

It says "PIC MIRROR PAGE" and has a bunch of ZIP files from 1995 to 2010.

Luck. Greetings.

Hello again

I am interested in add me to my small test bench and thinking in the advantage of several small digital instruments that are very good projects to save space.

Even though I have my old analog oscilloscope that doesn't look very good due to bad conditions, the slow synchronism is difficult to pinpoint the frequency range. But I have never been able to buy a new fast digital oscilloscope because it is expensive.

If you use the fast digital oscilloscope to take photos or video, you can help me with this project or you don't want to. Thanks.

There are three versions of digital frequency meter:

Low-Cost 50 MHz Frequency Meter (EPE Magazine September 2006) with PIC16F84 at 4 MHz, 1x MC10116 and 1x 74HC132.

Low-Cost 50 MHz Frequency Meter Mk.2 (EPE Magazine November 2008) with PIC16F628A at 4 MHz, 1x MC10116 and 1x 74HC132.

Compact 8-Digit Frequency Meter (EPE Magazine September 2017) with PIC16F88 at 4 MHz, 3x ADA4899 and 1x 74LVC2G132.

However, I find it difficult to get an old MC10116 IC because it appears "obsolete", and the problem is also that the ECL 10K family consumes much power.

My solution: remove this MC10116 and just connect it to the transistor?

I also don't have any ADA4899 nor 74LVC2G132. I always have several 74HC.

The HCMOS gates family datasheet shows input rise and fall times which are typical 8ns at 5V and 6ns at 6V.

In the case, I assume that each edge of the input signal delays 6-8 ns. It delays each rising edge at 6-8 ns and each falling edge at 6-8 ns. For double the pulse delay, it's 12-16 ns, I calculate 1/12 ns = 83.33 MHz (typical 80 MHz) and 1/16 ns = 62.5 MHz (typical 60 MHz). Does it mean that the symmetrical pulse period of 12-16 ns can disappear completely?

Then, for triple the pulse delay, it's 18-24 ns, I calculate 1/18 ns = 55.56 MHz (typical 55 MHz) and 1/24 ns = 41.67 MHz (typical 40 MHz). Because this datasheet does not show any maximum frequency.

My question is do you know what maximum frequency HCMOS reaches. Up to 40, 50, 60 or 80 MHz?

In another case, I go up to 6V from the regulator for 6 ns and I take into account that the output of the HCMOS gate at 6V to the input of the PIC at 5V so that it burns?

So, the conversion connects a resistor or double NPN/PNP transistor to 5V to the PIC input. But I don't know how the conversion is done.

Hope it solution a new simple conversion.

Before I make my new digital frequency counter design with PIC16F84 (in this case MPLAB ASM will calculate the number of bytes to record it) and 74HC132. I will finish it soon.

I will acknowledge some bugs that will be corrected.

See you.


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod