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I'm looking for an IC that I can use as a synthesizer. I want to build a circuit that uses a microprocessors A/D converter (the analog being a real world input, say like a push button), and the output of the microprocessor would be a voltage that changes the frequency of an oscillator circuit. I want that VCO part in an IC. Does anyone know what I could possibly use for this? It'd be really spectacular if this IC could have a few different oscillators.

Thanks for any help.

Moustache_Bash wrote:I'm looking for an IC that I can use as a synthesizer.

these exist in all shapes and sizes

Moustache_Bash wrote:I want to build a circuit that uses a microprocessors A/D converter (the analog being a real world input, say like a push button)

buttons get connected to digital inputs on a microcontroller. when you need more buttons for only a few pins, you use shift registers as a parallel to serial input converter. the parallel part is your buttons in groups of 8 for each shift register. you chain the shift registers together in series and you send serial data to the microcontroller on just 3 pins. there is another way where you actually do use the analog input on the microcontroller but it requires a resister per key and it is more laggy, harder to configure both in hardware and in software.

Moustache_Bash wrote:the output of the microprocessor would be a voltage that changes the frequency of an oscillator circuit. I want that VCO part in an IC.

are you looking for a digital or an analog oscillator IC? I think you mean that you want digital like a microcontroller. it does not make sense to have two microcontrollers connected by an analog control line. they are better at passing information to each other as serial data. better yet you can do this whole project in one atmega328P or atmega32U but I would probably suggest this

http://www.pjrc.com/store/teensypp_pins.html
http://www.pjrc.com/store/socket_20x1.html
^ 2 of these sockets

if I were you, I would build it in a socket to make it easier to program and also so you can re-use it if you make another prototype.

the keyboard interface with serial output is the DIN (digital input) modules made of shift registers from the midibox project. you only need this if your microcontroller does not have enough pins to use as inputs. so you probably don't even need it. but if you did you would need two for 64 buttons. each DIN module is 32 inputs.

http://www.ucapps.de/mbhp_din.html

available to purchase here
http://www.midibox-shop.com/buy.html
or
http://www.mikes-elektronikseite.de/mshop_englisch/


keep in mind you need to write the software and design some of the hardware. good luck with that. alternatively, this whole project can be done in analog but I don't have time to show you everything with that. either way. this is a very big project if your not building something word for word from some pre-existing kit or project.

analog VCO IC
http://www.aliexpress.com/item/ICL8038CCPD-ICL8038-DIP-14PIN-IC-IC-s-NEW/735260508.html
http://www.aliexpress.com/item/Sale-of-new-XR2206CP-imported-original-Advantage-supply-price-XR2206/886913143.html
http://www.aliexpress.com/item/1pcs-LM566CN-LM566-Voltage-Controlled-Oscillator-IC-m/655259334.html

this one has a serial input so it needs an attiny45 at minimum or maybe an arduino. also, the output is based on a 10bit DAC so not really %100 analog but it is kind self contained VCO IC.
http://www.aliexpress.com/item/New-AD9850-DDS-Signal-Generator-Module-0-40MHz-Test-Equipment-11635-01-01/729753256.html

here is another AVR synthesizer project. there are many.
http://www.elby-designs.com/contents/en-us/p710.html

Sorry, I don't communicate well. What I'm wanting to build is a circuit that uses a microcontroller that outputs a voltage to control a VCO. Sooo, I guess:
Pushbutton Input>Microcontroller>Outputs Voltage>VCO is thus tuned by this output voltage.

I have a pretty good idea how I'm going to write the code, so I won't need help with that. I do appreciate the input you're giving me, though.

SO, the VCO I decided I will use is this simple 555:


From what I understand R2, and the capacitor make up the frequency range. I plan on using a 4.7uf cap and a 15K resistor, which is about 14 Hz at it's lowest. Which is lower than the hearing range, but whatever I just need to be able to get to 20.6 Hz (a low E0). Then I want my highest note to be a B7, 3951.07 Hz. I'm assuming I won't be able to get that frequency range with a 0-5V input (input voltage to the VCO/output of the microcontroller, it can only output up to 5V) with just the cap and resistor I previously mentioned. So, I'll build a couple different oscillators with different RC networks to accommodate that limitation. Only thing I need to figure out is how to predict what the frequency output will be with a given input voltage to the VCO.

In that specific picture I posted (it's from a blog that I found randomly on google images), they state that:

=
T=w+0.693R2C

I'm not sure what T or w stand for in their equations I'm only familiar with omega, w=2piF.

Anyways, just thought I'd post findings as I stumble just in case someone might find some of this garbage of use or if anybody want to give some feedback/input.

Are you wanting pitch accuracy? That's the tricky thing with VCOs. Temperature, part tolerance, linearity (ie how constant is voltage vs frequency?) play a big part , I've tried and failed haha . But that said if it's just a general noise toy it don't matter

Yeah, I was wanting to do pitch accuracy. I was thinking of doing (all push buttons) a full octave set, then an octave plus a fifth, an octave above the previous set, an octave plus a fifth. It's just a project for school, so I'm just trying to communicate/implement my ideas. I'm okay with it, if it doesn't work. I'm just trying to learn and experiment. What I wanted to originally use as a VCO was a CDC9171, but they're now obsolete and I'm having a hard time wrapping my stupid brains around how I would use the various PLLs that are out there.

Since I don't know how to apply math to this specific situation, I think I'm just gonna hook it up to an oscilloscope and see what voltages will give me the frequencies I want. I guess I'll just kind of shotgun it.

Also, I'd love to hear about your experimentation's! Do tell.

you should just go to electro-music and search for "VCO schematic" or "simple VCO"

this is one of the best 555 circuits for accurate 1v/octave tracking. you can drop all the stuff you dont need. all the extra inputs.

http://electro-music.com/forum/topic-54623.html

I already saw that one, problem is I'm not smart enough for it. Like, all I need is a VCO In and an output.

this is pretty much the only thing that exists that is just an IC with no external components at all

https://sites.google.com/site/hearnmorley/products/hmvco1b

how do you plan to power it? are you a new to the idea of bipolar power supplies?

check out thomas henry's designs and books.

smallsnd/bigsnd wrote:check out thomas henry's designs and books.

I posted the thomas henry 555 VCO that is so damn simple and look what happened

books are your friends - which is why i posted about the thomas henry books.
reading will give you some of that knowledge you're lacking and will make you more confident in the circuit, rather than just staring at a schematic without having a clue as to what is going on.

the henry 555 VCO can be broken down to a simpler circuit if you'd like since a lot of the extra components are there for shaping the waveform, etc.
for example, on the main schematic you'll need the opamp and bipolar transistor pair on the left as they are for the voltage control, but if you can get by with just a triangle wave then you can ditch the ramp shaping stuff at the bottom of the main schematic as well as the entire 2nd page (except for the power section)

eatyourguitar wrote:I posted the thomas henry 555 VCO that is so damn simple and look what happened