Author Topic: Continuity tester circuit  (Read 4892 times)

0 Members and 1 Guest are viewing this topic.

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #25 on: July 17, 2021, 12:46:35 pm »
Just looking back through the thread, I might have spotted it earlier, but you could have used one half of the LM358 for the bridge input circuit from the Everyday Electronics project, and the second half for the bleeper oscillator, lifted as-is from the Not1Xor1 circuit. No need for the TL431 or the CD40106.  :D

You draw it.... I'll build it ;-)
If god had meant for humans to solder, she'd have given us three hands.
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: Continuity tester circuit
« Reply #26 on: July 17, 2021, 01:08:29 pm »
You draw it.... I'll build it ;-)

Now it's not that hard, It would be much more beneficial if you drew it and asked for corrections.  ;)

Take everything to the left of the output of IC1 from the, again, nicely documented, EE article (you don't need C3 as the LM358 is unity gain stable) and patch on everything to the right of the output of IC2/a (including D4) from Not1Xor1's design.
Best Regards, Chris
 

Offline iMo

  • Super Contributor
  • ***
  • Posts: 4675
  • Country: nr
  • It's important to try new things..
Re: Continuity tester circuit
« Reply #27 on: July 17, 2021, 01:33:34 pm »
I built myself (as a child) a continuity tester made of a single 40106 chip.
A standard single gate oscillator, where probes were placed instead of the timing resistor (in the RC part).
The probes were protected by series resistors and anti-serial zener diodes.
The other gates were used as a buffer for a piezo element. Powered from a single CR2032 (no power switch) forever..
When the probes were loose it produced maybe 1 tick a second or two. With probes shorted it beeped with a few kHz, thus I could judge on the resistance of the circuit based on the tone :)
« Last Edit: July 18, 2021, 09:04:44 am by imo »
 

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #28 on: July 17, 2021, 02:28:20 pm »
Now it's not that hard, It would be much more beneficial if you drew it and asked for corrections.  ;)

Take everything to the left of the output of IC1 from the, again, nicely documented, EE article (you don't need C3 as the LM358 is unity gain stable) and patch on everything to the right of the output of IC2/a (including D4) from Not1Xor1's design.

Not that hard for you... maybe! I'm just about to crack open BBox 1 and start learning electronics. I can just about read the diagrams, get the bits and wire it together. I'm not yet at the stage where I can understand to the point where I can create my own circuits. I can throw kits together, but don't ask me how or why they work. If something doesn't work when I've built it, I've got no skills to troubleshoot it.

For years, I've been bodging things together and hoping they don't go bang. How I've made it this far without causing a fire, I don't know. Probably by sticking to 5v DC at a guess  :-DD So yes, some way down the road I'd be happy to take on the challenge. Right now, however, I'm not up to the task.
If god had meant for humans to solder, she'd have given us three hands.
 

Online bdunham7

  • Super Contributor
  • ***
  • Posts: 7729
  • Country: us
Re: Continuity tester circuit
« Reply #29 on: July 17, 2021, 02:46:59 pm »
The problem you have with using this method with a DMM for continuity testing is:

1). Any shunt resistor below, say, 150R is going to continuously sound the DMM continuity bleeper - annoying, and the OP wants audible continuity testing.

2). Energised circuit protection.

It works in my case because I have selectable thresholds in addition to a readout of the resistance.  With a 10R shunt and 1R threshold selected, it works like a normal, audible continuity tester.  With a fixed 150R threshold and 1mA current, you'd need to use a 200R resistor.  This would keep things below the semiconductor threshold, but not the dry-contact/bad connection threshold of 20mV or so.

In my case this is an easily inserted and removed shunt that I only use when appropriate.  If I were concerned about protection, I'd only have to protect the shunt itself, as the meter is fully protected.  I'd probably look for a small light bulb with a cold resistance between 10 and 20 ohms. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Online bdunham7

  • Super Contributor
  • ***
  • Posts: 7729
  • Country: us
Re: Continuity tester circuit
« Reply #30 on: July 17, 2021, 03:12:42 pm »
One reason field techs love the antique Bach-Simpson 260 is Rx1 test current is almost 130mA at 1.5V which guarantees the reading involves copper - not water, rust etc.
I've had lots of multimeters give bogus ohmmeter readings on wire and cables with their piddly 0.3-0.8mA test current of the 200R range.

I have one and also a BK lo-hi resistance tester that uses up to a 200mA current on the low ranges and up to 1000VDC on the megohm ranges.  Neither one is very good for scanning DRAM modules for shorts. 

Quote
Even low voltage automotive, like trailer wiring it's pretty easy to bump 12V.

I made a powered test probe for automotive almost 30 years ago and the solution is still the best I've seen.  It's commercially available, just not as popular as I would have expected.  You supply the probe with +12V and ground, use an LM7805 with a 100R or so shunt to ground and then one of those bidirectional Red/Green LEDs (as big as you can find, or multiples) to the probe end.  Green = ground, Red = power, dark = open.

You need different instruments for different purposes.  That's why we all have stacks and boxes of various test gear, right?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline floobydust

  • Super Contributor
  • ***
  • Posts: 6927
  • Country: ca
Re: Continuity tester circuit
« Reply #31 on: July 17, 2021, 04:38:20 pm »
I didn't realize this continuity tester is for in-circuit use, based on OP.
So the requirements are test voltage under 0.3V and current under 5mA? Could just add a switch for hi/low test.
I like it when the LED is analog, can show varying resistance (brightness) verses on/off with a comparator. You can "see" the bad connection or poor probe connection.

The TL431 pinout is given as top view, which is awkward for TO-92. On-semi datasheet TL431 less confusing.
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: Continuity tester circuit
« Reply #32 on: July 17, 2021, 05:51:16 pm »
Now it's not that hard, It would be much more beneficial if you drew it and asked for corrections.  ;)

Take everything to the left of the output of IC1 from the, again, nicely documented, EE article (you don't need C3 as the LM358 is unity gain stable) and patch on everything to the right of the output of IC2/a (including D4) from Not1Xor1's design.

Not that hard for you... maybe! I'm just about to crack open BBox 1 and start learning electronics. I can just about read the diagrams, get the bits and wire it together. I'm not yet at the stage where I can understand to the point where I can create my own circuits. I can throw kits together, but don't ask me how or why they work. If something doesn't work when I've built it, I've got no skills to troubleshoot it.

For years, I've been bodging things together and hoping they don't go bang. How I've made it this far without causing a fire, I don't know. Probably by sticking to 5v DC at a guess  :-DD So yes, some way down the road I'd be happy to take on the challenge. Right now, however, I'm not up to the task.

Sorry for overestimating your position on the learning curve (or maybe deliberately setting you a bit of a stretch goal ;)). The 'cut and shut' is literally what I put in my post anyway. It just takes the audio oscillator part the Not1Xor1 design and uses it with the Everyday Electronics one as you have an opamp spare (half an LM358) and you probably don't have a CD40106. At the end of the day, battery consumption is a little bit higher but that doesn't matter.

The reason I pushed the Everyday Electronics one is (as I keep banging on about), it has a good low level description of how it works, how it was designed, and why components were chosen, apart from just being a good one. Back in the golden days, Everyday Electronics was launched as a beginners version of Practical Electronics which launched in the mid '60s. They needed another one for the people who hadn't 'grown up' with PE (which is where many of us oldies got the bug).

Luckily you can read the full set of issues for free. At your knowledge level a lot of fundamental things haven't changed (if you ignore the arrival of the micro, Arduinos etc), and most of the 'old faithfuls (like the LM358) are still available. EE and PE eventually got merged into EPE which still lives today, although a lot of the articles are reprints from the Australian Silicon Chip magazine, which seems in rather better health.

I really would recommend that you dig into the old EE issues, they had lots of bottom of the learning curve projects and teaching series (analogue and digital) which are just as relevant today, and are far better written than a lot of patchy, superficial web content you get these days....

https://worldradiohistory.com/Everyday_Electronics.htm

P.S. You can find PE, earlier EPEs and other mags there too.

EDIT: Just a note that safety standards have changed over the years if you are looking a any of the mains related projects!
« Last Edit: July 17, 2021, 06:21:04 pm by Gyro »
Best Regards, Chris
 
The following users thanked this post: floobydust, msknight

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #33 on: July 17, 2021, 07:14:21 pm »
Sorry for overestimating your position on the learning curve (or maybe deliberately setting you a bit of a stretch goal ;)).

I'll get there :-) ... At the moment I have the BBox1 and 2 ... box 2 came with about 80% of the bits needed including the LM358 (Box 2 has about three of them, and more than ten 555) - https://bitsnblobs.com/ - unfortunately they're not selling the kits at the moment. I also have, as I was advised, an early edition of Malvino, which I'm looking forward to. The BBox 1 has loads of bits and pieces including a prototyping board, battery boxes, LED's, a few diodes, resistors, capacitors... I'm heading in to a well laid out learning curve. Coupled with the mixture of parts I bought in the Velleman kits, I'm actually feeling confident about going forward and learning.

I did have a run in with one of the EPE issues... advised to me by someone I bumped into in a supermarket and overheard him talking... but when it came to the radio article all I could buy was the PCB. When it came to the other bits I was totally on my own and to an initiate like me, trying to track parts on some of these web sites was just too much. Almost put me off for life. In fact, what you say about it being reprints of older Australian articles, now makes sense on why it all fell to rats. There were parts in the list that I still can't get hold of, and some of which I had to find on fleabay.

I am fairly good at following rote, however, so I've re-capped a walkman and also a boom box...


 - dead easy to go through the board, identify the caps, finally learned how to order them, and got the job done. But if it had failed, I'd have been off the deep end.

I'm still bashing my head against a brick wall :-)
« Last Edit: July 17, 2021, 07:42:02 pm by msknight »
If god had meant for humans to solder, she'd have given us three hands.
 

Offline PA4TIM

  • Super Contributor
  • ***
  • Posts: 1161
  • Country: nl
  • instruments are like rabbits, they multiply fast
    • PA4TIMs shelter for orphan measurement stuff
Re: Continuity tester circuit
« Reply #34 on: July 18, 2021, 01:47:14 pm »
I made this one a few years ago: http://kripton2035.free.fr/Continuity%20Meters/ed-ultimateconti.html Works very well, very low voltage because there is no voltage with open test leads (the oscillator starts when you short the input) and it only uses 1,5V. No powerswitch needed and I used the 200 ohm potmeter. This way you can set the range of resistance. The higher the resistance the higher the tone. I can set it so it covers 0 to over 100 ohm but also 0 to 5 ohm, or even less.
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
www.schneiderelectronicsrepair.nl  repair of test and calibration equipment
https://www.youtube.com/user/pa4tim my youtube channel
 

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #35 on: July 18, 2021, 02:27:09 pm »
I made this one a few years ago: http://kripton2035.free.fr/Continuity%20Meters/ed-ultimateconti.html

I did see that one, and the links to the circuit design were not working, and a discussion about whether or not it worked. Obviously, it is working for you. I might try it.
If god had meant for humans to solder, she'd have given us three hands.
 

Offline PA4TIM

  • Super Contributor
  • ***
  • Posts: 1161
  • Country: nl
  • instruments are like rabbits, they multiply fast
    • PA4TIMs shelter for orphan measurement stuff
Re: Continuity tester circuit
« Reply #36 on: July 18, 2021, 02:58:11 pm »
I first made it with 2 smd transistors and it looked like it did not work. But using the oscilloscoop it worked but at a very high frequency (>50 kHz) . I then replaced the transistors by through hole ones (BSX20 and BC558)
This caused the oscillations to be lower but still to high. I then took my drawer of speakers/buzzers etc and that solved the problem. I then selected the loudest one that gave the wanted frequency range. The thing I used is a 3cm diameter metal speaker, I think it came out something like a postcard, the ones that makes music if you unfold it. But in that drawer there are piezospeakers, magnettic speakers, piezobuzzers etc, I am not into audio so I do not know all the types and just tried which one worked best (some did not work at all). The speaker I used gave sound if I connected it to a function generator zo it is some type off speaker and not a DC powered buzzer.

This speaker "problem" can be the cause it does not work for everybody. Often the problem with these sort of simple analog circuits is that it is sensitive for voodoo. But to be serious, as soon as things need to oscillate and you do not use a buffered and more or less isolated oscillator then everything in your circuit can and will influence the oscillator. But that is needed for this circuit. You want the oscillator frequency to change by the impedance of the circuit you are probing.

« Last Edit: July 18, 2021, 03:00:11 pm by PA4TIM »
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
www.schneiderelectronicsrepair.nl  repair of test and calibration equipment
https://www.youtube.com/user/pa4tim my youtube channel
 
The following users thanked this post: kripton2035, msknight

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #37 on: July 18, 2021, 03:15:51 pm »
This is interesting. The 1N5400 doesn't seem to be around but the 1N5408 is listed as a replacement and I have some of those. I also read that the BC547 and BC557 can replace the 548 and 558 respectively. I have those. All I would need is the 200 ohm pot (which is listed optional) and the 1w fuse resistor and I can build this. And a range of buzzers, of course. - that is if the replacements are valid.
If god had meant for humans to solder, she'd have given us three hands.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19345
  • Country: gb
  • 0999
Re: Continuity tester circuit
« Reply #38 on: July 19, 2021, 03:46:22 pm »
What's wrong with a piezo buzzer and a 9V battery? I suppose it's too basic and no fun.  :P

Here's a buzzer circuit I designed awhile ago. It will work off a single AA cell, down to 1V. I have built it before and it definitely works. A cheap 8 Ohm speaker will do.


Here's an improved version of the comparator-based circuit. If a micropower comparator is used for U1, it can be left connected to a couple of AAA cells, without draining the batteries. The tripping voltage is below the forward voltage of a silicon diode. It goes beeps, when Rtest <100R, but doesn't stop beeping, until Rtest > 200R, which provides some noise immunity. The trigger resistance is roughly equal to R4/100 and the resistance, when the buzzer stops sounding is roughly double that. I haven't actually built this circuit, but it should work, as long as a low power piezo buzzer is used, which can work down to 2V.
« Last Edit: July 19, 2021, 03:49:18 pm by Zero999 »
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: Continuity tester circuit
« Reply #39 on: July 19, 2021, 04:11:54 pm »
Here's an improved version of the comparator-based circuit. If a micropower comparator is used for U1, it can be left connected to a couple of AAA cells, without draining the batteries. The tripping voltage is below the forward voltage of a silicon diode. It goes beeps, when Rtest <100R, but doesn't stop beeping, until Rtest > 200R, which provides some noise immunity. The trigger resistance is roughly equal to R4/100 and the resistance, when the buzzer stops sounding is roughly double that. I haven't actually built this circuit, but it should work, as long as a low power piezo buzzer is used, which can work down to 2V.

Not wanting to be picky, but isn't that roughly the sort of threshold you get with an ordinary dmm continuity bleeper. If you're making one, it would be nice to have one that was more functional than what you already have. Admittedly the hysteresis might be nice.

P.S. The stumbling block, as far as I can understand it, is that the OP wants to go with what they already have (LM358?) or the TL431s on order, so I guess, no micropower comparators.
« Last Edit: July 19, 2021, 04:16:28 pm by Gyro »
Best Regards, Chris
 

Offline Gyro

  • Super Contributor
  • ***
  • Posts: 9410
  • Country: gb
Re: Continuity tester circuit
« Reply #40 on: July 19, 2021, 05:19:42 pm »
Now it's not that hard, It would be much more beneficial if you drew it and asked for corrections.  ;)

Take everything to the left of the output of IC1 from the, again, nicely documented, EE article (you don't need C3 as the LM358 is unity gain stable) and patch on everything to the right of the output of IC2/a (including D4) from Not1Xor1's design.

Not that hard for you... maybe! I'm just about to crack open BBox 1 and start learning electronics. I can just about read the diagrams, get the bits and wire it together. I'm not yet at the stage where I can understand to the point where I can create my own circuits. I can throw kits together, but don't ask me how or why they work. If something doesn't work when I've built it, I've got no skills to troubleshoot it.

If you really have difficulty following my written explanation, then I have chopped up the Everyday Electronics and Not1Xor1 designs, as I described, to use a single LM358. I'll leave the printing and glueing  to you....

Edit: LM358 pin numbers corrected.
« Last Edit: July 19, 2021, 05:46:32 pm by Gyro »
Best Regards, Chris
 
The following users thanked this post: msknight

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19345
  • Country: gb
  • 0999
Re: Continuity tester circuit
« Reply #41 on: July 19, 2021, 08:01:07 pm »
Here's an improved version of the comparator-based circuit. If a micropower comparator is used for U1, it can be left connected to a couple of AAA cells, without draining the batteries. The tripping voltage is below the forward voltage of a silicon diode. It goes beeps, when Rtest <100R, but doesn't stop beeping, until Rtest > 200R, which provides some noise immunity. The trigger resistance is roughly equal to R4/100 and the resistance, when the buzzer stops sounding is roughly double that. I haven't actually built this circuit, but it should work, as long as a low power piezo buzzer is used, which can work down to 2V.

Not wanting to be picky, but isn't that roughly the sort of threshold you get with an ordinary dmm continuity bleeper. If you're making one, it would be nice to have one that was more functional than what you already have. Admittedly the hysteresis might be nice.

P.S. The stumbling block, as far as I can understand it, is that the OP wants to go with what they already have (LM358?) or the TL431s on order, so I guess, no micropower comparators.
As far as I'm concerned, being able to leave it switched on indefinitely, without discharging the batteries, is a big enough advantage. The threshold could be altered by changing R4, which could be achieved rotary switch for preset values, or a potentiometer.


The attached (well written) project from an old 1989 copy of Everyday Electronics does the job well. It puts out less than 300mV on the probes and can be set to resolve to below 1R. It also has an isolation mode which checks for insulation above 1M. It has audible indication and decent protection against accidentally applied voltages.

Can I use an LM358L in place of the LM308 on that circuit, do you think? I have some of the former already.
Do you mean the LM358LV, or just the ordinary LM358? The LM358LV is a low power version, which would enable the circuit to be designed so it can be connected continuously, giving a standby battery life of a few years, from a couple of AA cells.
 

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #42 on: July 20, 2021, 08:36:43 am »
Do you mean the LM358LV, or just the ordinary LM358? The LM358LV is a low power version, which would enable the circuit to be designed so it can be connected continuously, giving a standby battery life of a few years, from a couple of AA cells.

It just has an L after the code.

I'm currently waiting for parts and it looks like the fusable resistor is going to beat the other bits by about a week... things appear to have got caught up in China, so that might determine which circuit I build.
If god had meant for humans to solder, she'd have given us three hands.
 

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #43 on: July 20, 2021, 09:57:34 am »
I think it might be LV - I've attached the best picture I can get of the codes...
If god had meant for humans to solder, she'd have given us three hands.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19345
  • Country: gb
  • 0999
Re: Continuity tester circuit
« Reply #44 on: July 20, 2021, 11:14:12 am »
I think it might be LV - I've attached the best picture I can get of the codes...
According to the LM358LV data sheet, it isn't made in through hole, so it must be the standard LM358.

Anyway, the good thing about the old LM358 is, its inputs can be taken to a higher voltage, than the supply, without being damaged, or drawing any current.  This means it should be possible to design a circuit which only powers the op-amp, when the probes are connected to something. The following circuit only powers the LM358, when the resistance across the probes falls below a few tens of kOhm. This means it can be left connected to the battery, without draining it, as long as the probes aren't connected to anything. It uses a buzzer, with a built-in driver circuit, for simplicity.


The spare op-amp in the LM358 can be used to make an oscillator, to drive a bare piezo transducer, which is a little cheaper and the tone can be varied, by changing C1 and R9, but it requires more parts.
« Last Edit: July 20, 2021, 11:17:08 am by Zero999 »
 

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #45 on: July 26, 2021, 06:58:47 am »
The design for the ultimate continuity tester calls for a 270nf capacitor. and I need through hole. I can find 220 and 330 in ceramic. I can't find 270 ceramic in anything other than surface mount. Do I use a 400v metallic film? How should I handle this please?
« Last Edit: July 26, 2021, 07:05:22 am by msknight »
If god had meant for humans to solder, she'd have given us three hands.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19345
  • Country: gb
  • 0999
Re: Continuity tester circuit
« Reply #46 on: July 26, 2021, 07:42:47 am »
The design for the ultimate continuity tester calls for a 270nf capacitor. and I need through hole. I can find 220 and 330 in ceramic. I can't find 270 ceramic in anything other than surface mount. Do I use a 400v metallic film? How should I handle this please?
Yes, 220nF or 330nF, 400V metallic film will be fine.
 
The following users thanked this post: msknight

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #47 on: July 26, 2021, 08:10:45 am »
Yes, 220nF or 330nF, 400V metallic film will be fine.

So by that token, I could use a 220nf or 330nf ceramic and not have to get a specific 270nf in metallic then?

If so... which would you recommend... 220 or 330... and why? - (never one to miss a learning opportunity)
If god had meant for humans to solder, she'd have given us three hands.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 19345
  • Country: gb
  • 0999
Re: Continuity tester circuit
« Reply #48 on: July 26, 2021, 08:50:49 am »
Yes, 220nF or 330nF, 400V metallic film will be fine.

So by that token, I could use a 220nf or 330nf ceramic and not have to get a specific 270nf in metallic then?

If so... which would you recommend... 220 or 330... and why? - (never one to miss a learning opportunity)
Both of those values are close enough. It will still work, but will oscillate at a slightly different frequency.

Electronic components are made in standard values, known as the E series of preferred numbers. The E3 series has three values per decade i.e. 10, 22 and 47, the E6 series six: 10, 15, 22, 33, 47 and 68. Most components have a velue equal to the E series multiplied by a factor of 10, which is why we see 10nF, 22nF and 47nF, but rarely 50nF. The reason for this is it makes no sense to specify a value of say 90nF for a component with a tolerance of 20%. It's much easier to say 100nF.

https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

Most of the time, it's normally acceptable to choose the nearest preferred value, unless it's a precision circuit, such as a volt meter, when changing a component value slightly, could significantly affect the result.
« Last Edit: January 27, 2023, 11:22:13 am by Zero999 »
 
The following users thanked this post: msknight

Offline msknightTopic starter

  • Regular Contributor
  • *
  • Posts: 190
  • Country: gb
    • My pages
Re: Continuity tester circuit
« Reply #49 on: July 26, 2021, 08:58:00 am »
Both of those values are close enough. It will still work, but will oscillate at a slightly different frequency.

Ah! Cool. ... so... if I read that right, I believe it will control the tone that comes out of the speaker... so a higher value capacitor should result in a lower tone generated. Am I reading that right please?
If god had meant for humans to solder, she'd have given us three hands.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf