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.
|Published (Last):||12 September 2006|
|PDF File Size:||15.36 Mb|
|ePub File Size:||6.40 Mb|
|Price:||Free* [*Free Regsitration Required]|
It needs to be at least 60X longer to allow the 74hx4051 of the pot and ‘ to slowly change the capacitor. All times are GMT. I’d recommend using only pF capacitance, or no capacitor at the A0 pin at all. When you change the 74HC control signals, the resistance of the pot plus resistance of the switch inside the 74HC begin slowly charging or discharging the capacitor.
74HC – Arduino, NodeMCU, Digispark and ESP
Tried to increase delay and it behaves more reliably now, I guess I should have included an image in the first place. Values over 1 nF really don’t make much difference. How do I calculate how large capacitor is needed? That’s contrary to the normal nonHC advice, where adding capacitance tends to improve analog measurement quality. 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.
I’m going to add a link from the MIDI page, since this is a problem that’s come up a few times. Without the rapid signal switching of a 74HC switch, the slowness of a big capacitor is still much faster than a human can move the pot. Please allow a few hours, I will rewrite it correctly when I’ll be at home after work.
You might also need to experiment with analog read averaging. For a more technical and correct answer, someone with more experience might have to fill me in. 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.
Always remember datasheets look like comprehensive technical specs, but they’re marketing material with a single purpose, to sell you the chip. In this circuit it looks like you’re running the 74HC from 5V. Even if the on resistance is about 4X that’d be my guess, based on my understanding of the transistors that 74uc4051 probably inside the chip 74yc4051, the pot is still the limiting factor.
I’ve updated the page to 74hc051 recommend HCT parts. You are right, the maths are correct, but I didn’t consider some resolution problems, please accept my apologies, I wrote that in a hurry. Hopefully it’s actually a 74HCT The reason for using the 74HC is that I’m planning to create a midi controller with around 50 pots and buttons, but I’m trying to get comfortable with the components first.
74HC – 8-Channel Analog Multiplexer/Demultiplexer
So even a 1 us delay ought to be enough. You might need to adjust the delay after the channel switching though and depending on how great resolution you need, you might have to implement some smart way to handle jitter in the readings.
No problem, thanks for your help. Obviously a big capacitor really slows things down. It does, but only if the capacitor has stabilized to the right voltage before you make the measurement. If you experience jittery readings I guess you could try and add it.
74HC4051 – 8-Channel Analog Multiplexer/Demultiplexer
Could larger pot values help? What values would be ideal for steady values at low delay? Here’s some explanation about why you need the delay, and how to calculate it. When I connect the pots direcly to two separate analog pins on the teensy, they seem to behave as expected. What’s happening here is the capacitor is storing charge which represents the voltage of the previously selected pot.
Thank you very much for the great explanation! Originally Posted by Theremingenieur. I’d done quite a bit of testing with different capacitors on Teensy 3. For example on row here: Is it possible to go lower the 74h4051 using too much current?
However, the two linear 10k pots I’m using seems to affect each other when connected through the 74HC I guess the 0. But I think the code should work. You can be pretty sure it’s not nice, since TI specs the part to 74hx4051 with as little as 2V power, but they don’t give any performance data below 4.
How much higher is a good question. Hopefully this lengthy explanation makes sense. The resistance of the switches will be higher when you have only 3. Added question about delay times.