switch that uses silicon gate CMOS technology to. – One Assembly and Test Site, One Fabrication achieve operating speeds similar to LSTTL, with the. Site. 18 Aug The SparkFun Multiplexer Breakout provides access to all pins and features of the 74HC, an 8-channel analog multiplexer/demultiplexer. 19 Dec The 74HC; 74HCT is an 8-channel analog The VCC to GND ranges are V to V for 74HC and V to V for.
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When you change the 74HC control signals, 74yc4051 resistance of the pot plus resistance of the switch inside the 74HC begin slowly charging or discharging the capacitor. Hi, I’ve got a follow up question on this.
They don’t say what it is at 3V, which is pretty typical of semiconductor vendors when a spec is really terrible. Page 1 of 2 1 2 Last Jump to page: Since you have between 0 to 5K from those 10K pots, the pot resistance when near the center of its range is the limiting factor. Originally Posted by loveaurell. Should it be as close to the pc power supply pin as possible? Anything less desirable is usually glossed over or just omitted.
74HC4051 – 8-Channel Analog Multiplexer/Demultiplexer
Is there something I have overlooked here? Thank you very much for the great explanation!
The worst case resistance is half the pot 74hc401, plus whatever the 74HC happens to be. But since it’s connected between vcc and ground, does it matter where in the circuit it’s positioned? Are there any drawbacks when using the 3. I just know what have worked for me. Originally Posted by PaulStoffregen.
What values would be ideal for steady values at low delay? Even if the on resistance is about 4X that’d be my guess, based on my understanding of the transistors that are probably inside the chipthe pot is still the limiting factor. It does, but only if the capacitor has stabilized to the right voltage before you make the measurement.
Hopefully this can save anyone else from such a frustrating problem. I have tried to replace the 74HC but got the same result. The 6, 7 and 8 pins on the 74HC are connected to ground. For a more technical and correct answer, someone with more experience might have to fill me in.
If you want to measure a large number of pots or other signals using a 74HC, obviously you 74uc4051 to keep those time constants short so you don’t need such a long delay. Heres a picture of my breadboard. The 74HC are not ideal switches for precision applications, they add a internal resistance of several hundreds of ohms depending on manufacturing tolerances, temperature and supply voltage in series with the connected potentiometer wiper which may have an impact on the results.
You can be pretty sure it’s not nice, since TI specs the part to run with as little as 2V power, but 74hc0451 don’t give any performance data below 4. I found out I got best results with a microsecons delay and an averaging of Of course, there’s always some capacitance.
You can never get zero error Ah, when I wrote above, there was no picture, so I was not aware of the capacitor. I’ve updated the page to also recommend HCT parts.
Without the rapid signal switching of a 74HC switch, the slowness of a big capacitor is still much faster than a human can move 74hhc4051 pot. When I connect the pots direcly to two separate analog pins on the teensy, they seem to behave as expected. All times are GMT. Originally Posted by Theremingenieur. Please allow a few hours, I will rewrite it correctly when I’ll be at home after work.
I am currently running with 48 pots.
I was hoping that It would provide enough precision for 7-bit values at least since it’s stated as an example here: How do I calculate how large capacitor is needed? Then, I would replace the nF by a 10nF capacitor to reduce the “charge change” time and you could go away with a us delay between switching the and doing analogRead.
Something to consider is the pot makes up most of the resistance that controls the speed. I need to know because I’m planning on using 1 74HC to run 6 buttons off one pin of the teensy’s digital pin and 7 more running on the analog pins.
74HC – Arduino, NodeMCU, Digispark and ESP
That’s contrary to the normal nonHC advice, where adding capacitance tends to improve analog measurement quality. The output of the 74HC is fed to A0, and digital pins 2 3 4 is controlling the channels on the 74HC You might also need to experiment with analog read averaging. Even the best capacitor will not solve all noise problems on the ground and the supply line which will occasionally cause “jumping” between two adjacent values, as does the ADC itself. Opps, make that delay closer to 4ms.
They also will consume 3. If It turns out that the 74HC is not the right tool for this, is there another way to expand the number of inputs of the teensy?