Circuit Bending

VTech Apple Part 5 – 555 Trigger Oscillator

Sam

circuit bending, loop trigger, 555

I have to admit for some time I have been stalled with my Vtech Alphabet Apple circuit bending project. I love the toy aesthetically and have always felt like there should be more bends available then what I was able to find. However even after hours of experimenting and dissecting this toy I was left feeling somewhat underwhelmed with the results. Over the weekend though I brought it back out determined to turn it into a more functional instrument, and to do that I needed to create a trigger oscillator.

If you want to get caught up before going forward don’t hesitate to visit my previous posts on this toy:

VTech Apple Part 1 – Kill Switch and Line Out

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Vtech Apple Part 3 – Voltage Starve

Vtech Apple Part 4 – Body Contacts

Since I hadn’t had any luck finding a loop on the board I moved on to less straight forward methods. I decided what I needed was a way to send a signal at repeating intervals to one of the contacts on the button matrix to trick the Vtech Apple into thinking a button was being repeatedly pressed and trigger a repeating sound. By generating this signal independently I could manipulate its frequency and control to suit my needs.

Once I had a clear definition of what I needed to get the job done the solution seemed all to clear, what I needed was a 555 timer. By setting up an astable 555 timer as a trigger oscillator I could route the square wave signal into the button matrix to repeatedly trigger the button (or buttons) of my choosing. Further by using a potentiometer I would be able to adjust the frequency of the square wave and therefore control the time between button presses as needed.

555 astable
This is a simple mock up of the circuit I used. Note that for this to work the positive voltage must be supplied by the toy itself and the ground must be share with the toy as well. This is easily accomplished by running the power from either the positive power connection on the Apple’s circuit board or directly from the kill switch installed in Part 1 . Just ensure it is connected at or past the kill switch so that the kill switch will remove power from the oscillator as well. Similarly the ground can be connected to any ground point on the circuit.

Astable 555 circuit
After testing my plan using a breadboard I put together this small 555 timer circuit on a scrap piece of perf board I had laying around from a previous project. I did my best to keep everything as small and compact as possible as my space inside the toy is somewhat limited. I’ve seen some circuit benders using what is called the “Dead Bug Method” in these situations to further minimize the size of the circuit. When building a dead bug circuit the components and connections are soldered directly to the pins on the IC rather than onto a piece of perf board. This can be an excellent way to shrink the circuit for those really tight fits but also leaves you with a more fragile product so since I could get away with using a board in this toy I did in order to get more stability and durability from the circuit. I will revisit dead bug circuits in a future post but in the interim there are many demonstrations of the method on YouTube if you deem it necessary.

Wiring 555 Oscillator
Once I had my 555  trigger oscillator circuit built the next step was to install it in my Vtech. I started out by planning positions and drilling holes for the potentiometer, switch and LED. Once these were in place I began the process of wiring the leads I had left on the 555 trigger oscillator circuit to their respective locations on the toy. On the diagram below I have marked the approximate paths of each wire upon installation. In planning this mod I did my best to limit the number of wires crossing between the back and front sections of the toy as these wires tend to get put under a lot of stress when the toy is being opened and closed. To achieve this I pulled power from my kill switch and sent ground directly to the negative terminal on the battery box. Since the switch and pot are mounted on the back portion this means only the pulse out wires have to cross over to the front half of the apple.

Wiring Vtech Apple

You may also notice that there are two pulse out wires leading from the switch to the button matrix. I used a 3 position on-off-on switch for this bend which allowed me to send the pulse to two locations based on the switch position (as well as nowhere in the off position) By connecting the opposing sides of the switch to different positions on the key matrix I am able to choose between two different buttons when running the oscillator. If you were so inclined and had the space to work with you could take this even further using a rotary switch or patch bay to allow you to select where the pulse was being sent. If there is a specific key you are after which you are not finding by touching the pulse to the solder points on the matrix try using your probe to connect sets of two points on the matrix together. If you find that this is necessary to get the input you desire this can be done by bridging the two points with a transistor and feeding the pulse into the base (more on that in a future article).

Finished Vtech Apple Loop
Once everything was wired I secured the 555 circuit and LED with hot glue, taped down all the loose wires and closed up the toy. I have to say after playing with it a bit I am really enjoying this modification. I’ve been able to produce a host of strange noises and effects and without having to use a hand to continually press the buttons I feel like I’m finally able to take full advantage of the other bends on this device. I’ve been having particular fun using the power starve to produce glitches in conjunction with the continuous oscillating noise produced by raising the rate of the 555 to high frequencies.

That’s all for today but I hope you guys have fun. Happy soldering!

Speak And Spell 2 – Pitch Bend and Hold

Sam

Pitch Bend and HoldAfter a lot of experimentation and some frustration I feel like I am beginning to wrap my head around the Speak and Spell’s operation. This is by far the most complex toy I’ve attempted to bend and as such there has been something of a learning curve as I explored the circuit and began manipulating it. That being said because this is such a popular toy for circuit bending I’ve been able to find a wealth of information to supplement my own experimentation and give me direction as I delve into this project. Today I’ll take you through the addition of a pitch bend up knob and a hold switch to my Speak and Spell.

Pitch Bend

Speak and Spell Pitch BendFor the pitch up bend I actually used three points, I initially found and started experimenting with the pitch bend using the two points on the board above (The 2nd and 4th pins from the right on the synthesizer chip) but found I was able to get a greater range by connecting the third lug on the potentiometer through a resistor to the point shown on the smaller board on the right side. I used a 100K pot and a 15K resistor though I recommend experimenting with different values until you find what works best for you.

Hold

wp-1467656667322.jpgHold and loop functions can be some of the most fun bends on any device as the allow you to create a constant repeating noise from the device which you can modify or play with in all kinds of ways and from my research into the speak and spell I understand it has a number of these type of bends available. Above is shown the first of these bends I was able to locate. If the switch is flipped while the device is making a noise it will continue to make that noise until it is flipped back down. You can then modify the noise output using the pitch bend.

Voltage Divider Tool

Sam

Voltage Divider Test Tool Today while trying to sort out the buffers on a voltage divider for one of my circuit bending projects I grew frustrated with the ever growing pile of alligator clips and random resistors/potentiometers piling up on my desk as I experimented with different values. To help alleviate this chaos I spent the last half hour or so putting together a basic tool to help simplify the process.

What this tool allows you to do is attach your voltage in (Vin) to the left screw using an alligator clip. Next attach the center screw to the point the divided voltage is going. Finally you can connect the rightmost screw to ground (Or some other lower reference voltage). You can then adjust the knobs on either side to find the approximate buffer needed for either side of the voltage divider to give you maximum play from the potentiometer you install on your project. This device can also be used as a basic bend tester by attaching your two bend points to the center screw and one of the outside ones to test different resistance values with the bend.

Voltage Divider Testing

You can also play with the potentiometer values or use additional potentiometers to give you an even wider range of values. I would have liked to include a 1 or 2 meg pot and a 10K pot to each side had I had them on hand to give the tool more versatility.

Voltage DividerAbove you can see the schematic for this tool, as you can see it is a fairly simple build. The connectors at the bottom represent the screws for attaching clips on the final project. Please note if you prefer you can use binding posts or banana jacks in place of the screws depending on what is most convenient for you.

Divider WiringHere is the final wiring of the tool

Speak And Spell Part 1 – Set-up and First Glitch

Sam

Kill Switch, Output, Glitch, Speak And Spell

Today I wanted to show you guys another circuit bending job I’ve been working on that I’m pretty exited about. I found a working Speak And Spell at a local Value Village recently and have begun exploring and cannibalizing its innards for my own amusement. If you’ve so much as googled circuit bending you are likely familiar with the speak and spell and what it’s capable of (not to mention its sister devices the Speak And Read and Speak And Math), These devices can be turned into incredibly effective electronic instruments. I have never worked with one before but I wanted to take you guys along with me for the ride and share with you my victories and mistakes as we turn this device into something awesome.

If your looking for in depth schematics and diagrams of the circuit and possible bends, Casper Electronics offers a lot of great information.

Kill Switch And Output

circuit bending

The first thing I did to prepare the device for bending was to add a kill switch along the power connection and a switched output jack from the speaker connection. As these modifications are identical to what I did on my Vtech Alphabet Apple I will not go into to much detail here. Note the Speak and Spell does feature an on board headphone jack which could be used in place of the output jack it you prefer but I like having 1/4 inch jacks on all of my devices so I added one anyway.

The First Glitch

Speak And Spell - Glitch 1

Next up was to start exploring the circuit, I began triggering sounds from the keypad while touching a pair of probes to different pins on the board. After a little bit of searching I had come up with one which spewed bits of gibberish or random tones when the points were touched. I attached two lengths of wire and experimented with a few different control methods before settling on attaching them with a button.

A Silly Mistake

Speak And Spell - Mistake

Those of you who have worked with Speak And Spells before may have already noticed it but I made rookie error with my first glitch. I am slightly embarrassed about it but wanted to share it as a cautionary tale. When choosing the location of the button I began drilling from the back thinking that I was clear of the keypad, but in my excitement I did not check to see how far clear of it I was. Sadly the hole I drilled damaged the key matrix and has stopped many of the keys on the left side of the keypad from working. Luckily, enough keys still work that I can still turn the device on and trigger lots of noises but it has interrupted normal function of the device. No more scary robot hangman for me…

Awesome LEDs

Sam

Vtech LEDs

Whether its a circuit bent monstrosity or a simple oscillator, nothing brings a project to life quite like a couple LEDs. Today I wanted to show you an easy trick I picked up from a friend to give the LEDs you add to your projects a clean and professional look without having to spring for fancy lights or sleeves. All you need is some hot glue, a shallow nut or washer and some electric tape.

Start out by drilling a hole where you want the LED to be, This hole should be bigger than the LED itself and around the same size or slightly larger than the hole in your nut or washer. Once the hole is drilled line the washer or nut up with it and place a piece of electric tape over it. Take a moment to ensure the electric tape is taught and smooth over the hole in the nut and that it did not move when you were taping it down (It should still be lined up with the hole in your project).

Next we want to turn over or open up the device and pour a generous amount of hot glue into the hole from the back, allow it to heap up a bit on the inside of your device, before the glue has a chance to solidify push the LED into the hot glue, do your best to stop it just shy of pressing into the tape on the other side so there is still some glue between it and the tape. Once it is in place allow the glue to dry for a few moments, If you would like you can take this opportunity to wire the LED to the circuit (If you haven’t already)

Once the glue has completely dried gently remove the tape, You may need to use an Exacto knife to remove any excess glue leaving a smooth surface filling the hole in the nut. Since the glue is translucent when the light is turned on the entire hot glue plug will glow giving the appearance of a large flat bulb.

 

VTech Apple Part 4 – Body Contacts

Sam

circuit bending vtech appleThe next stop on our circuit bending exploration of the Vtech Apple is going to be to add some body contacts. I really love body contacts as a control method as you can get a lot of range and really interesting tremolo effects with very little effort. The bend I’ll be adding them to is a second pitch modification I found while exploring the circuit. Oddly enough this bend seems to change between modifying the pitch up and down dependent on which mode the toy is set to (using the worm on the right side), On the modes where it lowers the pitch you can get extremely low droning noises using the body contacts which I’ve been really enjoying.

VTech Apple Part 1 – Kill Switch and Line Out

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Vtech Apple Part 3 – Voltage Starve

Vtech Apple Part 5 – 555 Trigger Oscillator

Vtech Apple - Body Contacts CircuitThe above photo shows the two solder points on the board I used to produce these effects, Once I had attached the wires I experimented with a number of different control methods and components including potentiometers, resistors with switches and buttons, and even strings of capacitors and LEDs (too see what would happen). I was able to create a number of strange effects but the one I found most interesting and which worked most consistently was body contacts.

Once I’d settled on a control method I drilled holes in the case and threaded 2 screws through them. Though I used screws on this project there are really limitless materials you can use to create body contacts. Any conductive piece of metal should work so it is really a matter of taste. Some examples I have seen used include thumb tacks, guitar strings, conductive tape, pennies or nuts and bolts, the possibilities are endless.

Vtech Apple - Body ContactsOnce you have the screws threaded in place you simply solder the wires onto them. I try to strip a longer portion of the wire than normal and wrap it around the screw to ensure maximum strength and conductivity. To finish it off I typically apply a healthy glob of hot glue over each screw (liquid electrical tape also works if you have it) to hold them in place and to make sure nothing inside the case comes in contact with them.

Now you can close up the case and start playing with them. Try using different fingers to touch the contacts or different hands, tap on one contact as you hold the other or slide you hand back and forth across them. Take notice of the slew of interesting ways you can now control your device and above all have fun.

Vtech Apple Part 3 – Voltage Starve

Sam

Circuit BendingAs I’ve been exploring and circuit bending my Vtech Apple toy I have unfortunately found a limited number of reliable glitches on the main board. Through my testing I have been able to cause the toy to output a slew of strange noises but have not found a bend so far which would do so reliably enough to warrant adding a switch or push button. Hope is not lost though, this just means we’ll have to be a little more creative and find other ways to turn this toy into the monstrosity it deserves to be. Today we will be adding a voltage starve to our apple which is another fairly simple mod which will limit the amount of power which enters the circuit with exciting results.

Vtech Apple Part 1 – Kill Switch And Line Out

Vtech Apple Part 2 – Exploration And Pitch Adjustment

Vtech Apple Part 4 – Body Contacts

Vtech Apple Part 5 – 555 Trigger Oscillator

Have you ever picked up a toy that’s been sitting around for a while, In a closet or at a thrift store and upon turning it on been greeted by demonic chanting or erratic glitches. This is because the batteries have become drained. As a typical battery gets low on power the voltage it outputs gets lower and lower until eventually it is to low to operate the device. With many devices though there is a sweet spot just before the voltage is too low to operate where the device will still run but isn’t able to do so normally, whether it slows the clock speed to almost nothing or just begins misfiring and glitching is dependent on the device and where in this sweet spot you are but the results can be extremely enjoyable. Through circuit bending we should be able to recreate this effect quite easily.

Warning – Though I have had good results with this bend on other toys I have found it to be quite unstable on the Vtech Alphabet Apple specifically. It does not seem to threaten the well being of the toy in any way (I’ve been using mine for quite a while and it still works great) but it can take a lot of finesse to get good glitches and may cause the device to crash. That being said once you’ve played with it for a while and gotten a good feeling of how far you can push it you can produce some fantastic effects through this mod, I definitely recommend giving it a try but don’t be discouraged if it takes a while to get a handle on it.

Circuit Bending Voltage Starve To recreate this effect we will add a switch and a potentiometer along the power wire between the battery and the main board. The switch will allow us to either send the power directly to the board (operates as normal) or through the potentiometer. The potentiometer will then add resistance into the power circuit which in turn lowers the amount of current which reaches the board. Typically a low value potentiometer is best for this but experiment with different values to find what works best. Sometimes having two pots in line is also useful, One high value pot for course adjustments and one small value one for fine tuning. Play around and find what works best for you.

Circuit BendingHere is a picture of the pot and switch once they have been wired into the circuit and mounted on the toy. Note in this photo the two red wires marked with the green arrow lead to the positive power connection on the main board and the single wire with the black arrow leads back to my kill switch and eventually to the battery. Now you should be able to close the toy back out and start playing with it.

Vtech Apple Part 2 – Exploration and Pitch Adjustment

Sam

circuit bendingIn Vtech Apple Part 1 I got started bending my new Apple toy by adding a kill switch and audio output. Now with those modifications in place we can really start to have fun with the circuit, today I’ll be taking you through some cursory circuit exploration and I’ll add my first bend to the circuit, a basic pitch/clock control. Before we get to far in though I’d like to go over the 2 main techniques I use to explore a circuit for possible bends :

Lick and Stick

This is something of a “wide brush” approach as it is not exact but can help to identify areas where bends will be possible. Typically the first thing I do when I open up a circuit is trigger a noise, lick one of my fingers and begin lightly pressing on different solder connections across the board. When doing this your finger will act as a connection between the points it touches (with a small amount of resistance added) and you should be able to start eliciting different reactions from the circuit. As you go mark down on a photograph or a piece of paper where you were able to get different effects from.

Probes

Once you have found some possible bend points it is time to refine and identify exactly which points you’ll be attaching wires to. To do this it is best to use a set of connected probes. If you do not have probes on hand you can make an impromptu set very easily by connecting two jewelers screw drivers with a set of alligator clips. Touch the probes to the different solder points you identified with the “lick and stick” method, To explore further options you can try placing different resistors or a potentiometer between the probes with alligator clips. Again mark down any bend points you identify on a photograph of the circuit or a piece of scrap paper.

Pitch Bend

Vtech Apple - Pitch Bend CircuitTypically the first bend I complete on a toy once I’ve explored the circuit is a basic pitch bend. On most toys the clock speed for the processor is set by a resistor placed somewhere on the board, through my exploration of the circuit I was able to identify that this was done using the resistor marked R1 on the bottom of the circuit board (highlighted above) when I bridged this resistor with my probes or with another smaller resistor the audio sped up substantially and the pitch rose.

From here I removed this resistor using my de-soldering tool and attached two lengths of wire, one from each end of where the resistor had been. Once these two wires are in place you can begin experimenting with different potentiometer values to find the one which works best. I will often also experiment with a rudimentary voltage divider by attaching the third lug on the potentiometer to ground which often gives you a wider range of pitch though I did not have success with that method on this particular toy. I ended up getting the best results using a 1M linear potentiometer. With this toy I also found whenever the potentiometer was turned to too low of a resistance the toy crashed. I was able to solve this problem by adding a 47K ohm resistor along one of the wires leading to the potentiometer to stop the resistance from ever dropping below that point.

Apple - Pitch Bend WiringOnce you’ve soldered the potentiometer and resistor in place you need only to drill a hole, fasten the pot in place and secure the wires. Close up the toy and you’re done, you’ve now got a pitch bend knob to modify the pitch and speed of your devices audio output. During my exploration I was able to identify a few more possible bend points so next time we can start getting into those and perhaps find an interesting way to fill the extra hole I made on the left side of the above picture. Until next time, Have Fun!

Vtech Apple Part 3 – Voltage Starve

VTech Apple Part 1 – Kill Switch and Line Out

Sam

Lately I’ve been playing around with circuit bending and wanted to share some of my progress with you as I have found it to be an interesting and rewarding way to create new and unique instruments. I will be posting more complex bends and projects in future but before we get too deep into circuit bending I wanted to quickly go over two simple modifications which I do to essentially every toy I bend. Today I’m going to add a simple kill switch and a switched output to my VTech Alphabet Apple toy. These modifications are a great way to start getting familiar with the circuitry of a new toy and can prove invaluable as you continue exploring and bending the circuit and developing it into a unique and bizarre noise machine.

Our Victim

VTECH Alphabet Apple untouched

Though these modifications should work on nearly any toy you decide to modify the victim I will be demonstrating them on is a VTECH Alphabet Apple which I purchased from a local thrift store for 4$. When choosing a toy to bend I like to visit the local thrift stores (Value Village, Salvation Army, Goodwill) for two reasons, first you can get great toys for outrageously cheap and second it’s the easiest way to find toys from the 80s, 90s and early 2000s which are by far the best for bending.   There have been several iterations of the Alphabet Apple produced by Vtech with a similar aesthetics but very different internal workings, this particular model seems to be the most popular and was released early in the year 2000.

The first step once you get the screws out and open up the toy is to take pictures, lots and lots of pictures, using a digital camera or phone. These photos will allow you to mark down any bends or notes you find down the road and can also be used as a reference if anything goes wrong. Often times the cheap solder joints attaching the wires in these toys can come disconnected and the photos can help you reattach them where they belong. Here i s a picture of the circuit from my Apple :

Apple Circuit

The Kill Switch

When we circuit bend a toy we are forcing it to operate well outside of the factory parameters and this can cause …problems. We are forcing the processor to run at unusual speeds and sending data in and out of the chip sets in ways that were never planned for. Often this will cause the system to crash or lock up which can often only be rectified by removing the batteries and allowing the circuit to reset itself. This can be time consuming and frustrating, especially if the battery compartment is difficult to reach or needs to be unscrewed to access.

To simplify this we will add a basic switch along the red positive power line to allow us the disconnect the batteries at the flick of a switch. Simply cut and solder the switch onto the power line, drill a hole in the casing and mount it as seen below :

Kill Switch

Adding An Output

Next up we will be adding an audio out jack, this will allow you to send the audio signals from your toy to a mixer, an amplifier, headphones or even effects and filters. One thing which consistently amazes me is the quality of sound you can often get from these toys once you bypass the cheap built in speaker and run them through a proper playback device, not to mention how much deeper or more interesting you can make the output by running it through a couple simple filters, or perhaps a guitar pedal or two, the possibilities really are endless.

Before we get started lets have a look at a quick schematic to get an idea of what we will be doing :

Line Out

As you can see above this is a fairly simple procedure, essentially we will be cutting the positive wire going from the main circuit board to the speaker and adding a SPDT (on-on) switch. This switch will allow us to either send the signal from the board to the speaker normally allowing the toy to be played via the built in speaker or to divert the signal to an output jack we have added which will effectively turn off the built in speaker and send the signal through to whatever we plug the toy into. From here the sleeve tab on the jack is connected back to the point where the speaker wire returns to the board thus completing the circuit.

The resistor placed across the jack is there as a safety measure, most speakers have a certain level of impedance which the circuit was designed to have while running (You may have heard speakers referred to as 8 ohm or 4 ohm speakers this refers to the impedance or “resistance” they place in the circuit) Since we’ve bypassed the speaker we have removed this impedance from the circuit and need to replace it with the resistor.

Before we wire this it is important to inspect the toy and decide where the switch and jack will be placed, I generally like to drill my holes and insert the components before doing the majority of my soldering but this is really a matter of personal taste and depends how tight a space you are working with. Be especially careful when placing the 1/4 inch jack, make sure to leave enough room behind it not just for the connectors on the plug but for the male 1/4 inch jack which will be inserted into it.

Output wiring

Once you’ve planned the location for the components you can wire them to the circuit. Take care to leave enough wire to reach from the board to the components without leaving an unnecessary amount of slack. The green and orange wires which are taped to the back of the keypad lead from the board (at the speaker output) down to the center pin of the switch and then from one of the outer pins of the switch back up to the positive side of the speaker. From the opposite outer pin of the switch you can see the small purple wire leading to the jack tab, the 10 ohm resistor across the jack and the second green wire leading from the ground (or sleeve) on the jack back to the audio return on the circuit board. Give it a test and you should be in business.

Now that we have these two simple modifications in place we are able to quickly cut power and reset the toy if we run into a crash or lock up, and we can pipe the audio from the toy directly into any other device which will accept an audio input. With only a handful of solder connections and four or five components we have transformed this simple toy into something much more versatile and have prepared it for the treachery we will soon be visiting upon it. Now the real fun can begin, Next time we will be looking at adding a pitch bend knob to the device and will begin searching for some glitches we can exploit to turn this “Learning Device” into an outlandish electronic instrument.

Click Here To Continue With Part 2