DIY Drum Kit with Circuit Bent Pedal Effects

I was down in my basement playing with a few of my older projects today and took a quick video to share with you all. In this video I use my 4017 based gate sequencer to control a set of circuit bent Kawasaki drum pads. I took advantage of the stereo output on the Kawasaki drum kit to use a stereo spliter cable to separate the left and right audio channels. I sent the left audio channel directly to my PA system while I ran the right through some circuit bent Danelectro pedals I had laying around. The result Is a clean channel and a distorted/echo channel which I can mix separately on my PA system. If you are interested in learning more about any of the projects used in this video don’t hesitate to visit the following links:

4017 Gate Sequencer
Kawasaki Drum Pad With Triggers
Circuit Bent Danelectro T-Bone Distortion
Circuit Bent Danelectro BLT Slap Echo

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Intro to Bipolar Power Supplies

As you begin to tackle more complex and interesting synthesizer components you may begin to encounter schematics for circuits which require both a positive and a negative power input to operate. As an example Eurorack synth modules use plus and minus 12V power supplies. As a result many DIY synth enthusiasts will also use +\- 12V so that they can interface with their Eurorack Modular set-ups. This is referred to as a bipolar power supply and is necessary for circuits which include operational amplifiers.

Unfortunately this can cause something of a tripping point for electronics or synthesizer beginners. When I first came across this it took me far longer than I like to admit to wrap my head around it. How could a voltage be negative? Do I need special equipment to power these circuits? This confusion was primarily caused by two misconceptions I held at the time:

Voltage is a measurement of force not quantity:
When we think about voltage we tend to think of it as a quantity. We assume that the voltage of a battery is the number of volts which that battery contains. This is perpetuated by the way we refer to voltage ; “This battery is 9V.” This is however not correct. The voltage we refer to with batteries, power supplies and circuits is actually the voltage difference between the positive and negative poles. If you are familiar with the water analogy for describing electricity you may have heard that voltage is the pressure which pushes the electricity through the circuit. If you had a pipe where you applied equal pressure to both ends the water would not move through it. If however you had a pipe where you applied a greater pressure to the water at one end of the pipe, the water would begin moving. Further the force with which the water moves through the pipe would be equivalent to the difference in pressure between the two ends of the pipe. Similarly with a 9V battery the voltage at the positive pole is 9V higher than the voltage at the negative pole which pushes the electricity from the positive pole, through your circuit, to the negative pole.

Consider then if you turned the circuit upside-down. This would mean the same 9V of force was still moving through the circuit. However now it is moving through the circuit in the opposite direction. The 9V of force would now be pulling electricity from the ground connection and pushing it to the power bus. This is what would be referred to as a negative voltage.

Ground is a reference point:
When I started working with electronics I did not have a firm grasp on what exactly ground was. I got used to using the negative pole of a battery as ground and began assuming that it was the lowest pole of the battery or power supply. This understanding served me fine with basic circuits but became a problem as I began working with op-amps and more complex circuitry. The truth of the matter is though that the ground is not an intrinsic point on the power supply and has more to do with the circuit itself than your power supply (That being said some power supplies include circuitry to anchor or shield their ground to make it more stable). The ground ultimately serves as a reference point from which the voltage of the circuit is measured. With some basic components you could set up a ground anywhere between the maximum voltage of your power source and 0V.

Consider the circuit above. The most intuitive way to approach this would be to say that ground is point C. In this case we would measure the voltage difference between B and C to determine that the voltage at point B is 9V. Similarly by measuring the voltage difference between A and C you can determine that the voltage at point A is 18V.

However if you approach the circuit differently you will see very different results. Lets say that we assign point B as ground in the circuit. In this case by measuring the voltage A and B to find that the voltage at point A is 9V. Next we would measure the voltage between C and B and find that the voltage at point C is negative 9V. This means the voltage at point C is 9V less than the voltage at ground (point B). The schematic shown above is the most basic bipolar power supply you can create and is perfect for developing familiarity with these types of circuits.

To make my life easier I soldered this small bipolar power supply together on a scrap of perf board I had on hand. I’ve added two large capacitors (330 uf electrolytic) to provide some decoupling for simple circuits. Additionally I placed leads on the positive, ground and negative traces so I could easily connect this supply to my breadboard.

If you are looking to free yourself from batteries I would strongly suggest looking into MFOs Wall Wart Bipolar Power Supply as an option for moving to a more permanent voltage source (along with the wonderful documentation provided with all of MFOs projects). Alternately if you have a traditional bench power supply there are many projects available to help you create a bipolar supply using the monopolar output these provide.

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555 Based Drone Synthesizer With LFOs

Today I have an update to the 555 Based Drone Synthesizer which I posted last week. I was having a lot of fun with my Drone synth but wanted to expand on it to get a bit more variation from the sound. To do this I added a set of LFOs to modulate the frequency of the drone oscillators.

To accomplish this I built a second set of three 555 based oscillators. These new oscillators are identical to the ones in the drone synthesizer except for a change to the capacitor between pin 2 and ground. By increasing this capacitor from 0.01uf to 1uf I was able to lower the frequency of the square wave they produce. This makes them perfect for use as LFOs.

I then connected the output (pin 3) of each of these new oscillators to the control voltage input (pin 5) of the corresponding oscillator in the drone synthesizer through a 1K resistor. An additional modification that can be made to this circuit to provide further control would be to replace this 1K resistor with a 10K or 50K ohm potentiometer which would allow you to modify the amount which the LFO modulates the oscillator in the drone synth.

In this experiment I have used LFOs but you could easily control the drone synth in other ways as well by providing a control voltage to pin 5. I am interested to see how this set-up would react to a control from a sequencer or keyboard and may try this in the future.

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Simple 555 Based Drone Synth

Today I have another very simple breadboard project based around the 555 timer. I’ve built three 555 astable oscillators similar to what I used in my 555 Serial Oscillator Project. This time however instead of connecting the oscillators in series I have run their square wave outputs through a simple mixer onto a single audio channel. This is known as a drone synthesizer.

As you can see from the schematic this drone synth is a fairly straightforward build. If you are familiar with 555 oscillators you probably recognize the layout of the 555 chips as a basic astable oscillator almost directly out of the 555’s datasheet. Once the three oscillators were created I added a 1K ohm resistor to the output of each (pin 3) and connected these outputs together. Once the three outputs are connected you can run this through a large capacitor (I used 330 uf) and out through your output jack. It is also possible to connect this circuit directly to a speaker though the audio level may be a bit low without amplification.

Once you’ve built this circuit you can begin experimenting with it. Pin 5 on the 555 chip can be used as a control voltage input so you could easily add a method of control voltage to this circuit. The easiest way to do this would be to build three more 555 oscillators and connect their outputs to pin 5 of the 555 chips in your drone synth. These will function as basic LFOs and modulate the frequency of the drone’s oscillators. You could also experiment with other voltage controls like a sequencer or keyboard. You could also replace one or more of the potentiometers with things like photo-resistors or body contacts to make the project even more interesting.

Lastly I wanted to mention that this drone synth is not limited to three oscillators. You can add as many 555 oscillators as you want in parallel to make an even deeper and stranger sound. If you’re interested in seeing the extreme of this a YouTube user by the name of Look Mum No Computer recently built a 100 Oscillator Drone that is definitely worth checking out.

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Atari Punk Console – Adding LFOs

Today I wanted to show you guys something new I’ve been playing with on the breadboard. Essentially what I have here is a twist on a classic project. I’ve taken an Atari Punk Console (Stepped Tone Generator) and added two 555 timer based oscillators as LFOs to add more depth and interest to the sounds produced.

This modification is built on one simple characteristic of the 555 timer (and by extension the 556 which consists of two 555 timers). This is the control voltage pin which allows you to use an external voltage source to modify the chips performance. On a traditional 555 timer the control voltage input is located on pin 5 while on the 556 you would use pins 3 and 11 as I have here. By connecting the outputs of two 555 oscillators to these pins on the 556 we are able to use them to modify the frequency of the stepped tone generator.

You may notice in the video I play mostly with the left LFO knob. This is because in my experimentation I was able to illicit much more noticeable effects from the first oscillator connected to pin 3 of the Atari Punk Console. The second oscillator (connected to pin 11) only seemed to have a pronounced effect at fairly high frequencies. For this reason you may want to try switching the 500K pot on the second oscillator for something smaller like a 100K or 50K. Another option to increase the frequency range is to change out the 3.3uf capacitor for a 0.1uf cap.

Another thing you can do with this circuit to gain further control is to add a potentiometer to control the modulation of the LFOs on the Atari Punk Console. To accomplish this you can add a potentiometer in place of the 10K resistor at the output of the LFO oscillators. A 50K pot would likely work best for this.

Finally if you enjoyed this project I did build an Atari Punk Console back in the early days of this site with jacks for control voltage inputs. Feel free to have a look if you are interested.

 

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Kidtunes Keyboard – Demo Video

I just recorded a quick video of my Kidtunes Keyboard project and wanted to share it with you. This project has been a lot of fun and I recommend it highly. I can’t wait to get an output jack added on so I can run it through an amplifier and see what it’s really capable of.

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Basic Bends – Kidtunes Electronic Keyboard

I’ve been working on a new toy and I wanted to give a quick update on my progress with it. Today I’ve been working on a Kidtunes Electronic Keyboard which I picked up at Value Village. The Kidtunes electric keyboard is made by a Chinese company called Scientific Toys and though I wasn’t able to find an exact year I would assume based on the circuit that it came out in the early 2000s. The keyboard itself is a little odd as it has two octaves (from G to F)  but is missing the second F sharp. I guess they assumed kids wouldn’t notice. The toy is monophonic (only one note can be played at a time) but has two distinct voices. There is a sustained organ voice as well as a shorter cleaner piano sound. The Kidtunes keyboard also features a demo mode and a low-high volume control.

One thing struck me as odd on the circuit board of this toy. It looks like, though they have used a black blob IC, they manufactured it separately and then added it onto the board. This has left easy access to the pins of the IC where it was connected to the main board. Though the majority of these solder points are triggers for the keys it still allows a level of access which is rare with modern toys. Additionally all of the components outside the main IC are though hole which allows for fairly easy bending and modification.

The first thing I added to this keyboard was a simple pitch bend. To do this I located the pitch resistor and removed it. On this toy the pitch resistor was located immediately below the IC. The resistor I removed was 220K ohm so I replaced it with a 100K ohm pot and a 150K ohm resistor in series. While playing with the pitch bend I also noticed I could illicit some very interesting glitches by attaching one of the legs of the pitch resistor through a capacitor to the base of a transistor on the far left of the board. I wired this up through a switch and moved on to see what else was available.

The next two bends I found were fairly straight forward point to point connections which I wired through switches. The first (red wires) involved connecting one of the resistors on the board to the trace running across the emitter of the transistor I mentioned in the pitch bend. This bend seems to impact the sustain of the Kidtunes keyboard. By connecting these points all sustain is removed so that the keyboard sounds like an xylophone. The second (yellow wires) connects one of the trigger points to a resistor on the board. When the keyboard is in organ mode this has the effect of holding any note played indefinitely when the switch is turned. Further in demo mode this will cause a note to play repeatedly. This second functionality will be extremely helpful while searching for further bends as I will no longer have to keep pressing keys.

That’s as far as I’ve gotten with this one so far. If I am able to find more I will be sure to provide an update. Also I should have a video of this toy online within the next day or so.

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555 Based Piezo Trigger

I’ve always been drawn to drum pads and kits. They are lots of fun and offer a slightly more tactile method of control then rows of pots and switches. So today while I was playing around on my breadboard I was drawn to pull out some piezoelectric disks and start experimenting.  What I’ve come up with is a very simple drum trigger circuit that you can build and experiment with.

This circuit uses a 555 timer set up in monostable mode. A monostable 555 timer will output a square wave pulse whenever it receives a trigger pulse from the piezo disc at pin 2. The pulse output from the 555 can then be adjusted through the 500K ohm pot placed between V+ and pin 7. The output pulse is then sent into the base of a 2N3904 transistor which works as a gate between the audio source and the speaker. This means when the pulse from the 555 is high the audio will pass through the transistor and when the pulse ends and the 555 output goes low the transistor will block the audio from passing.

If you are interested in adjusting the pulse length beyond what is available using the pot this can be achieved by adjusting the electrolytic capacitor between pin 6 and ground. By lowering the value of this cap you can shorten the range of pulse lengths available. Conversely by increasing it you can access a longer range of pulses.

By setting up 4 or 5 of these piezo trigger circuits you could create a fairly versatile set of drum pads. Since the audio source can be switched out or developed further there’s a lot that you can do to expand on the acoustic possibilities of your drum kit. You can try experimenting with different oscillators, Filters, LFOs, White Noise Generators or anything you want.

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555 Oscillators in Series

I’ve been spending a lot of time lately playing around with 555 timer chips and wanted to quickly share my latest creation. This project uses four 555 timers each set up as a standard astable oscillator. I’ve then connected the output from pin 3 of each oscillator to the control voltage at pin 5 of the next subsequent chip. Essentially this means each 555 timer is working as an LFO for the next oscillator to it’s right. I also increased the size of the capacitor between pin 6 and ground of the two left-most oscillators in order to  lower their frequency.

I was quite pleased with the range and depth of sounds it produced however, it should be said that I built this as a proof of concept and it is not fully flushed out. I would be very interested to try a similar setup with a different waveform. I feel like this idea would really come into it’s own if used with a triangle or sine wave oscillator which produced a wider range of tones. I have also been experimenting, with some success, with adding capacitors between the output and control voltage inputs to smooth the square wave slightly and create a saw tooth pattern. Without an oscilloscope on hand however this is proving difficult to optimize.

This is also a circuit which can be easily expanded by adding additional oscillators and admittedly there is a little voice screaming in my head to take it to it’s logical conclusion. I expect in my near future I’ll spend a rainy afternoon stringing together as many 555 circuits as I can fit on my breadboards and see what I end up with. I’ll be sure to share the results.

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Young Scientist – 320 Project Lab


This past week I was taking my usual trip through my local Value Village thrift store when I came upon something really rather cool that I wanted to share with you guys. Tucked at the back of a shelf in the toy section I found this Young Scientist 320 Projects Lab. I was shocked when I opened it up to find this kit not only to be in working condition but that most if not all of the components were still present in the box, including the numerous IC chips (more on them later). I decided for 6.99 Canadian how could I lose and brought the project lab home for to try it out.

I’ve only been able to find very limited information on the 320 projects kit or the Young Scientist brand itself. For this reason I can’t say exactly when it was released or the products history but based on the “Laptop PC styled” case and the windows 95-esc graphics on the lid I would assume the kit came out some time in the mid to late 90s.

I have played with a number of other electronic kits through my life and generally have mixed feelings about them. Kits like Snap Circuits or many Radio Shack’s 200 in one, 150 in 1 ect. offer a great introduction to circuits and basic components, however they always left me wanting. Once you have completed the projects designed for the kit there is nothing left to do and the box finds itself gathering dust. Though the knowledge you gain through these projects is invaluable there is no easy way to transition from them into further electronics work.

The Young Scientist 320 Project Kit seems to have a slightly different philosophy. The usual spring connectors we know from Radio Shack kits are present but they are secondary. They are organized around a breadboard placed dead in the center of the kit. This kit uses standard through hole components the same as the ones you would use in any hobby electronics project. This means you can build and solder together any project from the kit onto protoboard and also build essentially any electronic circuit within the kit. Further within the instruction manual it encourages “Young Scientists” to expand their component collections and even gives some basic instructions for salvaging parts.

Another exciting feature of this kit can be found on the breadboard and that is the power supply. The power rail of this breadboard is split into 6 sections providing easy access to a full range of common voltages (1.5, 3, 4.5, 6, 7.5 and 9).

The kit also included a number of IC chips. Again these are standard through hole components the same as you would use in any hobby project. There was no surprise in finding the hobbyist heavyweight 555 timer along with some standard op-amp and amplifier chips but I was pleased to discover the set also contained a fairly complete array of digital logic gates, counters and decoders. The inclusion of these digital components allows for some extremely complex builds towards the end of the project book including Function Generators, Logic Probes, various games and Octave Generators (just to name a few).

As an adult with hobby electronics experience I am loving this kit but I should say in closing that it is not for everyone. The decision to use standard through hole components and a breadboard makes this a far more versatile project lab than others I have worked with and allows for the construction of far more complex projects but it is a double edged knife. If you are an absolute beginner to electronics the smaller more fiddly parts can be confusing or challenging to work with and the level of difficulty in many of the projects could be discouraging. For this reason this is lab is likely better suited to someone with some knowledge of electronics, components, resistor codes ect. Still, If you have some basic knowledge or are up for the challenge, a project lab like this one can be a great way to build your skill level and play with hundreds of new and interesting circuits.

 

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