Hi all,
I am totally new to this and extremely excited. I have some medium programming knowledge and have been soldering here and there and I believe I can go ahead and try to do something nice with the Teensy.
I am set to build a one way only (for the now because it is simpler) modular midi to usb device. The goal is to maximise the analog ins with 4067s.
[Edit: I ended up using 4051 as Paul repeatedly mentions them I figured they might have been safer for a newbie]
I understand I will have to start small and grow as I get confidence as many say. That is fine.
Before I embark on this journey I would love to hear some suggestions about what I understood and what I haven’t, and I guess the list of my question could be very well used as a FAQ for total noobs.
I am totally new to this and extremely excited. I have some medium programming knowledge and have been soldering here and there and I believe I can go ahead and try to do something nice with the Teensy.
I am set to build a one way only (for the now because it is simpler) modular midi to usb device. The goal is to maximise the analog ins with 4067s.
[Edit: I ended up using 4051 as Paul repeatedly mentions them I figured they might have been safer for a newbie]
I understand I will have to start small and grow as I get confidence as many say. That is fine.
Before I embark on this journey I would love to hear some suggestions about what I understood and what I haven’t, and I guess the list of my question could be very well used as a FAQ for total noobs.
- the recommended impedance for linear potentiometers is 10k ohms. Higher values add precision but more noise, lower values have less noise but less precision. Right or wrong?
- If one is set to use tons of potentiometer (32,64,128,256,..) wouldn’t be appropriate to use 5ks (or less) to reduce the noise given that for midi we only need 7 bits resolution?
- Is there any sense in having a potentiometer with a higher mW value? I see the majority being 250 mW or 500mW, are the latter to be preferred?
- Considering distance, noise and cables: in general, is it better to have the mux closer to the teensy or to the pots? Since I’d like to make it modular, I’m thinking of using widespread 5 pins din connectors to the modules which would host the potentiometers and the mux.
- Potentiometers are to be connected in parallel and not in series, and directly to the teensy even when interfacing with a mux. Right? (That makes the soldering more difficult though).
- It is not recommended to solder directly on the pins and use headers instead.
- On the software side: the delay needed to read properly a mux is negligible for non time critical applications (such as a midi controller). The loops in the software will run fast enough to be well within tolerable latencies (let’s say 2ms or the likes) even with a number of muxes connected to the same 4 digital pins.
- To manage eventual noise there are two main solutions:
a. add capacitors between the input and ground of the potentiometers (or something like that, apologies!). This would require added latency to the reading of each mux channel of about 1ms though.
b. use analogReadAveraging in the code - Besides having a custom pcb built, is it better to use a breadboard to connect components or there is noticeable degrade compared to manual soldering (let’s consider the soldering might not be at super professional level). Is using tons of female/male - cable - female/male wirings considerable?
- How would you recommend soldering so many things in parallel (to the 3.3 pin for instance)?
- Wires: am I totally wrong in thinking that the thickest and more shielded the better as long as you can solder the head/fit it into female headers? As a thought experiment let’s suppose I connected a 3A 220v standard solid wire fro the pot output to the analog pin. Would that make sense (besides being overkill?)
- The 3.3 to pots wire (considering a single wire to a 5pin connector which will then go to the pots in parallel should be larger right?
- There are tons of 4067s with different other codes/letters in catalogues. Are they all sort of similar or should I really pay attention to part numbers etc. You guys all seem to mention it as just a 4067 variating from HC to HCT to the BE at the end. Apologies for the very stupid question.
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