23
votes
How can 16 buttons be connected with only 8 wires?
How can this work without any multiplexer?
It doesn't. The keypad board seems to have just switches, with maybe some diodes we can't see. However, the left board looks like it has a processor on it....
- 315k
21
votes
Accepted
19
votes
How to read input from multiple (dozens) of sensors, with fewer pins
Dozens of temperature/humidity sensors sounds like a set of greenhouses, eventually with servos to open windows or run pumps ...
If you have dozens of anything, modularity and testability are really ...
- 16.2k
14
votes
Accepted
How can I control 8 LEDs using only 5 pins of a microcontroller?
8 leds on/off have 2^8 = 256 possible states
5 control pins on/off have 2^5 = 32 possible states
Since 32 < 256, and you can't use shift registers or i/o expanders, it would be impossible...
But if ...
- 1,454
13
votes
Accepted
Control one relay via multiple 12 V DC signals
Since you need isolation, you will need a relay for each appliance.
Even if you didn't strictly need the isolation, it would be recommended since it might be hard to safely share the same voltage (...
- 2,181
11
votes
Reading a huge number of analog sensors in real time
The obvious answer is muxing, this means that you make electric path's dynamically. So just iterate through the whole matrix, one at a time, or as many ADC (Analog to Digital Converter) inputs as you ...
- 8,249
11
votes
Accepted
What does INH as an IC pin label mean?
They are representing that signal as active-high Inhibit (INH), which is logically equivalent to active-low Enable (EN#).
- 15.1k
10
votes
How can I control 8 LEDs using only 5 pins of a microcontroller?
Use addressable LEDs like WS2812B or similar.
You’d need only 1 pin (plus power and ground) to control hundreds of them. They are available individually or as part of an LED strip (which can usually ...
- 1,213
10
votes
Steer multiple LEDs with one microcontroller pin
Upgrade you MCU to one with more pins. It will be cheaper than adding more parts.
- 1,194
9
votes
Accepted
What is the purpose of diodes in flip-dot displays?
If we redraw your circuit without the diodes, we have this:
simulate this circuit – Schematic created using CircuitLab
Now imagine you drive Column-1 High and Row-1 Low (and Column-2 and Row-2 ...
- 14.8k
9
votes
How can 16 buttons be connected with only 8 wires?
Without diodes... you'll get phantom rectangles.
For instance in your example (2,2) (2,3), (3,2), and (3,3); you chose an ironic example by choosing a rectangle. If you actually press all four, it ...
9
votes
Accepted
What is the difference between an analogue multiplexer and digital multiplexer?
The operation of any multiplexer (MUX for short) is conceptually the same, be it analog or digital.
In essence you have a set of numbered data inputs (usually a power of 2, say \$N=2^n\$ inputs named,...
9
votes
What is the main difference between a decoder and a demultiplexer?
They're nearly the same thing. A decoder selects one of n outputs based on a set of select lines.
If the decoder device also has an enable, the decoder can be used to send a signal (the enable state) ...
- 58.2k
9
votes
What is the main difference between a decoder and a demultiplexer?
A demultiplexer (demux) can be an analogue circuit or a digital circuit. It has a select input value (usually binary), one signal input and multiple signal outputs. It routes the signal input to a ...
- 23.8k
8
votes
Difference between i2c switch and i2c mux
The two chips are NOT the same:
The TCA9544A is an I2C Mux. An I2C Mux multiplexes any one of N downstream ports to the upstream port (1 to 1).
The TCA9546A is an I2C Switch. An I2C Switch ...
- 81
8
votes
Accepted
Analog Mux as Cheap I2C Mux?
Analog multiplexers work just fine for I²C signals (if you keep the impedance and parasitic cpacitance small enough, which is usually not a problem).
I²C multiplexers are more complex because they ...
- 20.1k
8
votes
Accepted
Not enough pins, looking for a "demultiplexer" that keeps state
What you are looking for is a GPIO "expander" chip. There are many available, typically using I2C or SPI to connect to the microcontroller. The Microchip MCP23017(I2C)/MCP23S17(SPI) is just one ...
- 178k
8
votes
What is this kind of "Multiplexer" called?
A digital encoder or Priority Encoder. They will often have \$2^n\$ inputs and \$n\$ outputs.
Additionally there will be an any-active output and an enable input.
You can combine multiple encoders ...
- 2,853
8
votes
Accepted
Is space division multiplexing really multiplexing?
Space Division Multiplexing sounds like snake-oil, but it's worth treating it as a topic for study, as there are costs and benefits when applying it.
It's defined as pushing several independent ...
- 174k
8
votes
Accepted
What does this schematic mean?
This notation means a bus line with the width noted by the number written next to it. In your case it is 2-bit wide bus. It is used to make the drawing less convoluted by reducing lines drawn.
- 10.1k
8
votes
Steer multiple LEDs with one microcontroller pin
Addressable RGB LED strips work with one single data pin.
- 172k
7
votes
Can rotary encoders be multiplexed?
Yes, but...
Yes, they can, it is simply a question about the sample rate.
You have to perform some calculations. You have to determine the maximum speed for which you want your encoders to function. ...
- 14.6k
7
votes
Accepted
Reading a huge number of analog sensors in real time
Depending on your price range, you may want to consider using an FPGA between your Raspberry Pi and ADCs, such as the DE0-Nano Board, which has good support as an introductory FPGA dev board. This ...
- 1,041
7
votes
Control one relay via multiple 12 V DC signals
When any appliance reaches a specified temperature, it sends out a continuous 12 VDC signal. This is intended to activate a relay to run a ventilation fan.
Then those 12 V signals are powerful enough ...
- 81.4k
7
votes
Accepted
Clipping when using a CD4051 analog multiplexer
It will work okay, in fact series resistance will be near minimum, but leakage will be relatively high (perhaps in the few uA range) increase at high junction temperature (perhaps >100uA at Tj=100°...
7
votes
Accepted
Using 1N4148 diodes on segments of multiplexed 7-segment LED display
You are correct in looking for the design decisions, and all the information you need is on hand.
From your schematic and an assumption that the segment currents are in the 25 mA range we can work out ...
- 22k
7
votes
Why don't analog multiplexers specify PSRR?
I don't think you could give an accurate PSRR without defining external circuitry, because the impedances of the circuit on both sides of the switch determine the effective rate. Instead, you get the ...
- 19.3k
7
votes
7-segment 4-digit display ghosting
You are turning two digits on at once by writing the 'or' first and then the &. The new one will have the segment drive for the old one on for a short period of time- enough to create perceptible ...
6
votes
Can rotary encoders be multiplexed?
If you're trying to use 64 encoders as "frob knobs", the more typical way of doing this is to use each encoder for multiple purposes, and have some way of controlling which purpose the knob is serving ...
- 30.6k
6
votes
Reading a huge number of analog sensors in real time
Three ideas:
1. Do some multiplexing on the supply side
Effectively, the circuit you've described is a large number of variable resistances each with one end commoned to a supply voltage. You want ...
- 1,488
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