9/8/2023 0 Comments Cd74hc4067 arduino![]() ![]() ![]() When doing so – take note of the limitations mentioned earlier – take some resistance measurements in your situation to determine what the maximum value will be from your ADC and calibrate code accordingly. In this example we connect the common pin to the board’s analog input pin – so this can be used as a method of reading sixteen analog signals (one at a time) using only one ADC. This is where we select one input pin of sixteen and allow current to flow through to the common pin (1). Pin 15 of the ‘4067 is set to GND, and control pins S0~S3 are connected to Arduino digital output pins D7~D4 respectively. For demonstration purposes we’re using an Arduino Uno-compatible board with the 74HC4067 running from a 5V supply voltage. Now to show an example of both multiplexing and demultiplexing. ![]() Finally, don’t try and run more than 25 mA of current through a pin. When a channel is active, and a 5V supply voltage, we measured a resistance of 56Ω without a load through that channel – and the data sheet shows other values depending on the current load and supply voltage. The next item of interest is the “ON” resistance – that is the resistance in Ohms (Ω) between one of the sixteen inputs/outputs and the common pin. The first two parameters show what the minimum voltage that can be considered as a HIGH and the maximum for a LOW depending on your supply voltage. Open you data sheet and consider the “DC Electrical Specifications” table. How you control those control pins is of course up to you – either with some digital logic circuit for your application or as mentioned earlier with a microcontroller.Īpart from the power supply requirements, there are a few limitations to keep in mind. For example, to select pin 9 (9 in binary is 1001) you set the IC pins S0 and S3 to HIGH, and S1 and S2 to LOW. If you scroll down a bit hopefully you noticed that the combination of S0~S3 is in fact the binary equivalent of the pin number – with the least significant bit first. nothing) it shows what combination of HIGH and LOW for the control pins are required to select which I/O pin the current will flow through. Not only does it show what happens when pin 15 is set to HIGH (i.e. So how does that work? Once again – reach for the the data sheet and review the following table: By setting these HIGH or LOW (Vcc or GND) you can control which I/O pins the current flow is directed through. Finally there are the four control pins – labelled S0~S3. The sixteen inputs/outputs are labelled I0~I15. This is where the current either flows in to be sent to one of the sixteen outputs – or where the current flows out from one of the sixteen inputs. You can always control this with a digital output pin if required, or just tie it to GND if this doesn’t matter. Pin 15 is used to turn the control the current flow through the inputs/outputs – if this is connected to Vcc the IC stops flow, and when connected to GND it allows flow. The power supply for the part is applied to pin 24, and GND to … pin 12. Next – consider the pinout diagram from the data sheet: If for some reason you have the 74 HCT4067 it can only work on 4.5~5.5V DC. The first thing to note is that the 74HC4067 can operate on voltages between 2 and 6V DC, which allows use with 3.3V and 5V microcontrollers and boards such as Arduino and Raspberry Pi. Another way to think abou it is that you can consider the 74HC4067 to be a digital replacement to those rotary switches that allow you to select one of sixteen positions.ĭon’t let that put you off, it’s just what we had in stock at the time. The part itself is available in through-hole and surface mount versions.Īt this point you should download the data sheet, as we refer to it through the course of the article. That’s a mouthful – however in simple form it’s an IC that can direct a flow of current in either direction from one pin to any one of sixteen pins. One example of this is the 74HC4067 16-channel analog multiplexer demultiplexer. Now and again there’s a need to expand the I/O capabilities of your chosen microcontroller, and instead of upgrading you can often use external parts to help solve the problem. ![]()
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