Electronics Lab Philippines

Electronic Bongos

Offline Super zHero

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Electronic Bongos
« on: April 01, 2020, 04:56:02 PM »
Finally, after two weeks of total "Blackout" from the World Wide Web, my internet is back  :)

So to keep my sanity at home (nag-iisa lang ako sa bahay, except for my cats), I dug up my old magazines and found the article in the copy of August 1977 Popular Electronics of the "Cabonga".


Offline Super zHero

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Re: Electronic Bongos
« Reply #1 on: April 01, 2020, 05:05:09 PM »
I've had this perf-board project sitting in my parts drawer since 2010.  I made it maybe in the late '70s right after the magazine article came out, got it to work, and never did anything of it after.

Stay put while I upload my photos and share this project with you.  It uplifted me these past few nights while locked-down here at home....


Offline Super zHero

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Re: Electronic Bongos
« Reply #2 on: April 01, 2020, 05:17:27 PM »
The article in the Aug 1977 Popular Electronics magazine came in two parts.  Unfortunately, I don't believe I bought the magazine with the second part.  But here it discussed the complete construction of the project.


Offline Super zHero

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Re: Electronic Bongos
« Reply #3 on: April 01, 2020, 05:45:04 PM »
This page shows the schematics and a PCB artwork.  While the Op-amp indicated was a 5558, I used an LM324 quad op-amp for my prototype.  You can use the more common LM358 which should be pin compatible with the 5558.


Offline Super zHero

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Re: Electronic Bongos
« Reply #4 on: April 01, 2020, 05:54:37 PM »
Page 3 of this article.



Note that the drum sensor is just a sensitive "touch" switch.

Offline Super zHero

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Re: Electronic Bongos
« Reply #5 on: April 01, 2020, 05:57:05 PM »
Last page of the article.


Offline Johannah Aleksandria

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Re: Electronic Bongos
« Reply #6 on: April 01, 2020, 07:47:19 PM »
single supply lang yata ang lm358? andami ko nito dati galing sa betamax, c358 ang tatak.
Generations come and generations go, but the world stays just the same. What has happened before will happen again.

Offline Super zHero

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Re: Electronic Bongos
« Reply #7 on: April 01, 2020, 07:53:39 PM »
If you are wondering why this project is under 'Analog Electronics', it's because it is Analog in nature.  Now in the days of microprocessors and 'purely' Digital, this project shows how we did it in the past.

I was surprised and very much elated in hearing the tunable Bongo drum sounds this produced connected to an amplifier.  I'm pretty sure I didn't hear it as such 40 years ago after I assembled my prototype.

Now I'm so inspired to continue and improve the assembly of this project.  I hope you can follow and have the same experience with me.

Offline Super zHero

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Re: Electronic Bongos
« Reply #8 on: April 01, 2020, 07:57:14 PM »
The LM358 may be used with dual supplies from +/-1.5V to +/-16V per National Semiconductor Datasheet.  Thanks for the comment.

Offline Johannah Aleksandria

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Re: Electronic Bongos
« Reply #9 on: April 01, 2020, 08:03:01 PM »
Ibig sabihin nyan sir kailangan mo ng 7 sets para sa complete drum set. O kaya hindi kayang gayahin ang cymbals?
Generations come and generations go, but the world stays just the same. What has happened before will happen again.

Offline Super zHero

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Re: Electronic Bongos
« Reply #10 on: April 01, 2020, 08:20:42 PM »
Imagine mo na lang nung unang panahon when all the circuits were like this- one or more oscillators per tone.  If you use digital switching, you can minimize the analog circuitry.

I like to also make cymbal and bell tones, which can be done.

Offline Super zHero

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Re: Electronic Bongos
« Reply #11 on: April 02, 2020, 10:42:46 AM »
Back in 1969-70, we bought an electronic organ (keyboard) and when I looked at the inside, there was a long line of LCR tone oscillators and filters for emulating different instruments.  Now-a-days tones and filters are performed by digital means.

Offline Super zHero

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Re: Electronic Bongos
« Reply #12 on: April 02, 2020, 11:08:24 AM »
I had built my experimental prototype using an LM324 quad opamp sufficient for two iterations of the circuit- oscillator and buffer amp.  The photo shows "mirror" circuitry on each side of the IC.  I had removed some components on one side so I can contain an onboard dual PS (which I obtained from eBay).



For the trigger I used a cheap N.O. pushbutton which does the job.

Offline Super zHero

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Re: Electronic Bongos
« Reply #13 on: April 02, 2020, 11:35:11 AM »
Here's the dual output PS I'm using.  It outputs +15V at 600mA and -15V at 120mA.  Input of ~3.3Vdc to 13Vdc with quiescent current of 3-4mA as specified, not as I tested.  So it's safe to use on battery power.



Offline Super zHero

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Re: Electronic Bongos
« Reply #14 on: April 02, 2020, 01:46:31 PM »
Let me take this moment to make a disclosure.  I am not a musician.  But as a male growing up in the '60s, music was a great part of our generation.  And in those days with the growth of the electronics industry and availability of electronics components to the common people including the youth, it was easy to delve into and experiment with electronic sounds and music.

This electronic project is a part of history and nostalgia.  I used to be an electronics professional but since I'm now retired, I'm just now an electronics hobbyist with a great interest in music.

Offline Super zHero

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Re: Electronic Bongos
« Reply #15 on: April 02, 2020, 02:25:17 PM »
Let me also take this opportunity to announce the demise of my beloved Tek oscilloscope model TDS 2002 which I've had for about 20 years.  If any of you can tell me if this can still be repaired, please reply on this section or PM me.  Thanks

I believe that the screen module just quit:



As you can see some color bars appeared and the overall contrast is poor.

So in this emergency, I quickly ordered an RS brand o'scope hoping I would get it in four day's time.  That was two weeks ago and after checking on the status of my order, they haven't sent it out yet  :-\

Offline Super zHero

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Re: Electronic Bongos
« Reply #16 on: April 02, 2020, 02:53:59 PM »

A quick discussion on how it works in a less technical manner.  Shown below is the heart of the circuit which gives it the tone.  It's called a twin-T filter (oscillator).  The filter components are below IC1B and the feedback components compose of R8 and R9.

The sound produced by this circuit is a damped sine wave.  R10 adjusts the frequency.  The oscillation is started or gated by a positive pulse from R3.



Offline Super zHero

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Re: Electronic Bongos
« Reply #17 on: April 02, 2020, 03:15:32 PM »
The pulse or gating voltage to the oscillator is produced by this circuit:



In this original design, depressing momentary button S1 which comes from +V on its right side (not shown), produces a single pulse.  No matter how short or how long you have this switch depressed, only one pulse will go to R3.

The disadvantage of using a switch is it is prone to switch bounce.  There is also no control on the pulse output as to how hard or soft you hit the drum head (no velocity) since the sensor is a plain ON/OFF switch.


Note J1 which is an external signal source jack.

Offline Super zHero

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Re: Electronic Bongos
« Reply #18 on: April 02, 2020, 03:27:42 PM »
The last part of the circuit is the buffer amp which is the other opamp of this dual opamp IC in the original circuit.



R11 is the volume control potentiometer.

Offline Super zHero

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Re: Electronic Bongos
« Reply #19 on: April 02, 2020, 03:35:33 PM »
In the coming days I will discuss my mods to this circuit.  I hope to get my oscilloscope the soonest time but in reality that would be at the end of this quarantine, or in three more weeks' time.

Meanwhile, if you have the parts, why not build this project to keep out the boredom at home.