Showing posts with label DIY. Show all posts
Showing posts with label DIY. Show all posts

Saturday, 25 January 2020

555 Timer IC

A bit about the 555 IC.
This is a very basic introduction for a friend who is learning electronics.
I'm building a NLC 555 resonator which uses five of these. This module provided the
prefect excuse to discuss it.

The 555 is the most popular integrated circuit ever manufactured.
It was developed by Signetics in 1972 and is found in timer, pulse generation, and oscillator applications.
The Atari Punk Console uses two of these (one in astable and the other monostable configurations)
or one 556 chip.
The standard IC is commonly known as the 555 timer, but it has many more applications than the name suggests.

There are a few variations of the original 555 ic.
The original were TTL (Transistor-Transistor Logic) or bipolar. These preceded modern CMOS chips
which use much less power. The TTLs use bipolar transistors.
The advantage of TTL is that they are hard to damage and have powerful outputs, but they can generate voltage spikes. In comparison, the CMOS versions don't spike, have less powerful outputs.
The 556 has two timing circuits.
The 558 has four timing circuits in one package.
There is very little standardization among manufacturers.
Sometimes you will see 7555s used instead of 555s
The Intersil ICM7555 is a low-power CMOS version but there are other CMOS versions with no clear
identifing marks.

The 555 IC has 4 operating modes:
1. Astable (free-running) mode
2. Monostable (one-shot) mode
3. Bistable (flip-flop) mode
4. Smitt Trigger (inverter) mode.

Astable Mode
An Astable Circuit has no stable state - hence the name "astable". ... It can also be used to flash lamps and LEDs, and is useful as a 'clock' pulse for other digital ICs and circuits
Here the 555 timer puts out a continuous stream of rectangular pulses at pin 3.
It's output is continually alternating between high (1) and low (0) and it never has a stable state.
The frequency of the pulses at the output  is controlled by an RC network (resistor capacitor)
made up of R1, R2 & C.
The frequency can be calculated with the formula:
F = 1.443/(C(R1+2R2))

Thus the larger the values of R1,R2 & C, the lower the frequency.
The 10nF capacitor connected to pin 5 is a decoupling capacitor to shunt electrical noise

Monostable
A Monostable Circuit produces one pulse of a set length in response to a trigger input (such as a push button). Here the 555 works as a timer (Monostable Multivibrator).
It's output has a stable logic state that only changes when the 555 is triggered or activated.
Normally, the output at pin 3 is low (0). It remains at this state until a low (0) is applied to pin 2 (trigger).
When this happens, the timer is activated and pin 3 goes high (1)...... but only for a certain amount
of time.
Notice that pins 7 and 6 are connected to each other and to C & R.
The time period when the pulse exiting pin 3 is high is determined by the values of R & C.
This time period can be calculated using the following formula:
Time ON = (1.1)(R)(C)

Thus , the larger the values of R & C, the longer the time ON.
The 10nF capacitor connected to pin 5 is a decoupling capacitor to shunt electrical noise, to avoid instability and false triggering.

Bistable (flip-flop) mode.
The full name is a Bistable Multivibrator.
Flipflops are really impt as they are the building blocks of sequential circuits such as counters, registers, decoders, latches, memory, etc etc....
Basically, they are memory circuits that remember the logic state they were set
You can read more about flip flops here:
+ Flip Flops - an introduction

The 555 timer can act as a SR flip-flop.

 (Author of image: Philip Bosma)

You need to put two pull up resistors on pins 4 & 2 to hold the voltage high.
The 10nF capacitor connected to pin 5 is a decoupling capacitor to shunt electrical noise, to avoid instability and false triggering.

For computer applications, the 555 is not very useful as a flip-flop as its output is relatively slow.
Computers are driven by very high speed clocks, and the trigger and reset response times can't keep up.
But it's ok for noncomputer applications where high-speed response isn’t necessary.

Smitt Trigger (inverter) mode.
This  converts a noisy  (analog) input into a clean digital output.
It's a comparator circuit.

 The input signal is connected through a capacitor which connects to the trigger and threshold pins.
The 10nF capacitor connected to pin 5 is a decoupling capacitor to shunt electrical noise, to avoid instability and false triggering.

Links
+ TTL - transistor-transistor logic  
+ DIY Index
+ CMOS
+ How did NASA steer the saturn V - the computer & data storage in the 1960s (memory module)
+ LVDC - The saturn V memory module
+ NLC It's 555 
+ Evil Mad Scientist
+ Collin's Lab: Atari Punk Console

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You can find more NLC builds here.
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Fates - a DIY Norms for Rasberry Pi

This page will be for my personal build notes.










There is a 18 week waiting time on the OLED display.
:-(
So This build may take a bit of time to finish

to be continued.....
-----------------------
 Download Fates disk image (for pi3 or pi4)
For Raspberry Pi 3b+ (191230 norns 2.2.6)


 download tthis
Use balenaEtcher - https://www.balena.io/etcher/

put on sd card
insert into the pi andppower up.

then set up wi fi
ignore  "norns wifi hotspot"

Open a terminal (on tthe PC) then SSH to the Pi
??????

The default norns user is we
The default password is sleep
Thus to connect you will use ssh we@norns.local (or the IP address of the device) and enter sleep

Set your timezone, wifi-country and expand filesystem

Open a terminal, SSH to the Pi and do
sudo raspi-config
first go to Localization Options menu item and select Change Timezone
then repeat with Change WiFi Country

stop !!!
the next part is super impt!!!!!!!
because unless you do this next step, fates will not recognise the rest of your disk.


Then go to Advanced Options and select the first option to Expand Filesystem
Finish and reboot (if not prompted).
(if you dont do this your card will think its full, and you wont be able to save anything.


After these changes, 2 things may happen:
  1. You get a SUPERCOLLIDER FAIL error at the top of the screen. In this case use the norns menu to SLEEP (which shuts the pi down) and then when the led stops flashing, unplug and plug in power once more to restart. At which point you should see option 2 below.
  2. You see NONE listed at the top of the screen. This is normal. Just go to SELECT > AWAKE to start the Awake script.

As of 12-30-2019 DO NOT run the on device SYSTEM > UPDATE from the norns menu.- otherwise this will 'brick' th Fates.

My friend Allinaire has a Fates installed in a performance case

One of the algorithms is based on the game of life.
Cellular Automatia


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Links
+ Main site
+ github
1.8V build
+ Build & BOM 1.8

Tuesday, 21 January 2020

It's 555 - Nonlinear Circuits 555 resonator - Build notes

These are my build notes for the 555 resonator eurorack module.
This module is inspired by Bernie Hutchins' CMTG or Cascaded-Monostable Type Generalized Resonator.  He described this in Electronotes #93, September 1978. 



I've got a couple of versions of this. .. in banana format and the early metal plate euro format.



This early one was mostly through hole.
The new module is SMD. I understand this is version 5.



Module description:
"it's 555..." resonator/drone/noise source with CV control of pulse width for all five stages (plus a CV all input)


This module takes an input signal and splits it into clusters of 5 independent pulses. The pulses are created whenever the signal transitions from negative to positive. Each pulse can have its width modulated by pot or CV and can be set to any amplitude or even inverted. The pulses are summed together at the output to give a rich strong signal, choc-full of harmonics. It is a very powerful sound that cuts through any mix.


Andrew adds in his build notes:
"this design is based on the Electronotes EN#93 Cascaded Monostable Generalized Resonator.
The main changes from the EN version are that it has been expanded to 5 stages and uses \
larger valued capacitors to allow the pulses to get wide enough to merge with each other and promote mayhem".

So whats a resonator?
According to wikipedia:
"A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at some frequencies, called resonant frequencies, than at other frequencies."

Below is a standard monostable configuration of a 555


And here is a small section of the resonator circuit.
This is repeated 4 more times and the output from pin 3 is cascaded into pin 2 of the next 555 chip.

From what I can decipher from the schematic the input pin of the 555 is pin two. This is pulled down.
The 10n cap connecting pins 7 and pin 6 is the timing capacitor. This is also connected to external CVs which I guess is how you get voltage control of the circuit.
The 10nF capacitor connected to pin 5 is a decoupling capacitor to shunt electrical noise, to avoid instability and false triggering.

You will need five 555 ICs


These are pretty easy to get on. Watch the orientation.




Next are  the BCM857
These are bipolar PNP matched transistors


Tricky to get on the pcb , and watch the orientation.
There is a dot on the top left


The BC847s are NPN matched transistors


The circuit uses four TL072 op-amps.
From what I can decipher from the schemo, one is part of the opening comparator circuit.

 The input enters here. I'm guessing that the identity of the input signal (apart from its frequency) is lost when it leaves the comparator. The output is just a trigger  for the following monostable 555s,

A second opamp is used as part of the voltage control.
And the last two find their way in the summing circuit ???











Links:
+ Wiki
+ BOM & Build notes
+ My build notes for the early Metal faceplate version
+ Op-amps - basic circuits
+ All about the 555 IC

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Click here to return to the NLC Build Index:
http://djjondent.blogspot.com.au/2015/03/non-linear-circuits-ncl-index.html


Wednesday, 25 December 2019

Potentiometers - Basic info for DIY synthesizers

"A potentiometer is a three-terminal resistor with a sliding or rotating contact
 that forms an adjustable voltage divider. 


 1 = input
 
2 = wiper
 
3 = Gnd 
 
Total Resistance = R1 + R2
If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat."
(wikipedia)
 In synths, usually terminal 3 is connected to ground.

They come in lots of shapes and sizes.
 Eg Slider, thumb, trim pots. 

Sliders are often called faders.
-----------------------------------------------------------
 Trimpots come in lots of shapes too.
They are meant for fine tuning, and to be adjusted infrequently.



Trimmer Marking  Value
PR1        102         1K
PR2         503        50K
PR4         203        20K 
PR140     104       100K



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 There are two main types of pots:
1. Logarithmic  or audio (A)
2. Linear (B) 

Linear
The resistance between the contact (wiper) and one end terminal is proportional to the distance between them. ... ie the angle of shaft rotation is proportional to the resistance.
Used mainly for CV (control voltage) pots

Logarithmic 
The resistive element follows a logarithmic taper.
Used alot in audio pots.

----------------

This is how you could set up an arduio Uno to measure the voltages from the wiper.
I'm using TinkerCad here for the simulation.


// set up variables
int myVoltPin=A2;
int readVal;
float V2;
 int delayT=250;


void setup()
{
  Serial.begin(9600);
}

void loop()
{
  readVal=analogRead(myVoltPin);
  V2=(5./1023.)*readVal;
  // converts to a voltage -- remember to place the decimal
  // points after the 5 & 1023 ... these may be floating points
  Serial.println(V2);
  delay(delayT);
}


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Saturday, 14 December 2019

DAFM synth - DIY build notes

My unofficial build notes for the DAFM synth.


I am in no way associated with the developer. These are just my personal build notes to help me trouble shoot, should I have any problems.
The 


The DAFM uses the YM2612(OPN2) and it's CMOS variant the YM3438.
The 2612 was used in arcade machines, the Sega Mega Drive/Genesis home game console (1988), and the Fujitsu FM Towns (1989)
It's a FM/PCM hybrid chip
The chip can have either 5 or 6 FM channels.
 (5 FM channels with 1 PCM or 6 channels without PCM)
   The YM2612 has six channels with four operators per channel.




tHE build is super easy. All parts are supplied and well labelled. If you can follow a recipe and know how to hold a soldering iron, you can build this.



 There are  8 algorithms. The envelopes, frequencies and LFOs can be changed to get a good range of FM sounds.

The midi section is on the top left. A standard DIN connector.
 Thats a MPR121 breakout pcb on the lower right.
It's a capacitive touch sensor controller driven by an I2C interface... probably what controls the cube keyboard.
Presets can be saved in the RAM memory or in a SD card as DMP files that can be opened with VGM trackers like Deflemask.


The top right section... LD33V power regulator & USB - type B, female.
The USB connector is  the power supply of the DAFM synth
The  LD33V powers the touch sensor


Also added the two lower encoders.
These are used to move through the DAFM Synth menus.

That pink board is the audio preamp.


The 8 MHz Crystal oscillator ... for the timing.
keep the dot on the bottom left.

This second pink PCB is a multiplexer.
It lies between the SD card & the DIN socket.

This TCA9548 I2C Multiplexer connects to the four OLED displays.
The four OLED displays share the same I2C address.


Next solder the four 0.96 I2C Monochrome OLED displays.


Now its time for the  STM32F103C8T6.
It's an arduino micro-controller of course






iT'S A wonderful thing when you see the synth power up on the first attempt.



Links
+ buy on tindie
+ Youtube - menu
+ Build instructions 
+ Wikipedia - YM2612 
+ Yamaha FM chips
+ Microcontroller Index Page
+ User guide
+ github - Genesynth   
+ Genesynth - blog
+ Genesynth - pjrc
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FM Index
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