Suggestions on how to control a display with a knob.

[Spork Schivago]

Hello,

I know this is probably going to sound like a real easy project for most of the users here. I'd like to start learning how to make some circuit boards again. I have a broken BGA Rework station that I could use to add BGA components to my projects. I have a hot air rework station for SMD components and I have a soldering iron for SMD / through hole components.

I'd like to stick with SMD components if I could. I think right now, my goal for this project is to have something like a 3 digit 7 segment display. I'd like to be able to control the digits on that 3 digit 7 segment LED display. For example, I'd like to have the display show 000. Then, I'd like to take a control knob and turn it and have the display go up a value. I'd like it to go from something like 000 to 300. I'd like it so the faster I turn the knob, the quicker the display changes.

I have a PIC programmer. What would be the best way to go about doing this?

Ultimately, the end goal is to modify the project so I can control the value with a computer via a USB cable or via the local area network (using ethernet cable, probably not wirelessly). I thought start small, work my way up. Any suggestions are welcomed. I don't want to use something like an Arduino though. I'd like to build the circuit from scratch. Thanks.

[stj]

Re: Suggestions on how to control a display with a knob.

use a rotary encoder, and start with the code used in the ESR meters - it's written in "C"
https://www.mikrocontroller.net/svnb...oftware/trunk/

[Spork Schivago]

Re: Suggestions on how to control a display with a knob.

Thanks Stj.

I was thinking of implementing something like i2c or SPI. I like the different idea. Eventually, I want to be able to control this device via USB or manually, using a dial (or maybe a keypad, or touch screen, I haven't decided yet). I gotta learn to walk before I start running though! Thanks.

[mariushm]

Re: Suggestions on how to control a display with a knob.

An alternative to rotary encoders could be capacitive / touch sensor chips.
You just make a rectangle area on a pcb and separate the copper into equal chunks and connect these chunks to the inputs of a capacitive sensor IC which is then able to detect when the finger touches the copper pads and some more advanced chips can detect and tell you that use swipes finger from one side to the other and tells you the swipe speed.

A very nice chip for example (though probably a bit complex for your needs) is CAP1214 from Microchip (they bought SMSC which designed this) : https://cdn.badcaps-static.com/pdfs/...bdf91afe23.pdf

It's a chip with 14 capacitive channels that can be used in a slider configuration or slider AND individual buttons , and the chip also has a driver for up to 11 leds (you can program driver to blink, dim, full on or off, link leds to individual input channels etc). Downside is it works on SMBUS (similar to i2c, so easy to code) but would add a lot of code to your microcontroller and so on.

There are other, much simpler chips out there, you can check out their datasheets and see how easy it would be to do it, here's a short selection : http://www.digikey.com/short/3j1mjq

Even if the chip works as buttons only, it's fairly easy to implement a slider mechanic in your code, just keep track of buttons pressed in a buffer and the time between presses and you know if button 1 is pressed, then button 2 is pressed and so on, you know user swipes from left to right.

PS. There are some PIC microcontrollers that have capacitive sensor built in, see http://www.microchip.com/ParamChartS...?branchID=1013 and scroll to the right and select on the capacitive column 4 channels or more.

[stj]

Re: Suggestions on how to control a display with a knob.

i wouldnt bother with that, you can just use an old synaptics pad from a busted laptop if you want touch.
doing PS2 serial comms on a pic is easy.

[Spork Schivago]

Re: Suggestions on how to control a display with a knob.

I'm going to play with a few ideas. I want to make my own BGA rework station, infrared. But right now, the idea is just to make the preheater. And to do that, I want to make the PID controller. But to do that, I want to figure out how I'm going to accept user input. I want something that's real nice. I want to make it open source and open hardware, so other people can contribute to make it better but also make their own.

I thought it'd be great learning experience too. I like the idea of touch screen, but I dunno, I like the idea of being able to have the user (me) just input a temp for the preheater and have the same screen maybe show the current temp, the set temp, etc. But that's a heck of a lot of work and I think money as well, to do it real nice, like the way I'd want it. I think right now, maybe the dial would be the way to go. I'll play with the rotary encoder for a bit. I'll order one. Then maybe I'll look into figuring out how to control the 3 digit (or 4) display with the PC using a USB cable or something. Thanks guys.

[stj]

Re: Suggestions on how to control a display with a knob.

to make a pid controller you should start by designing a thermocouple input circuit.
that's the tricky bit.

i dont think an 8 or 16bit mcu will be good enough in the end either.

[rhomanski]

Re: Suggestions on how to control a display with a knob.

The only problem I have with touch screens is ham fisted people using them. Some try to use a pen, some use filthy fingers, it's a struggle to keep them clean and useable.

[Spork Schivago]

Re: Suggestions on how to control a display with a knob.

The only problem I have with touch screens is ham fisted people using them. Some try to use a pen, some use filthy fingers, it's a struggle to keep them clean and useable.

Yeah, that's a good point. I think no matter what way I go, there's always going to be some pro's and some con's, you know? The idea, I think, is looking at the pro's and con's and trying to figure which one best suits my needs. Thanks for pointing out the touch screen stuff.

[stj]

Re: Suggestions on how to control a display with a knob.

probably best to work out how the menu's will work before you decide on the interface.

if you just want to scroll up & down a menu then a rotary is best.
if you are entering numbers for example, a touchscreen is best.

[Spork Schivago]

Re: Suggestions on how to control a display with a knob.

I thought because it's going to be open hardware, it'd be cool to get ideas from other people. I thought one thing that should be thought about is how it's physically going to look. I like the modular design idea best I think. You know, separate preheater, separate PCB holder, separate top heater. Then people could mix and match. Let's say you want hot air for the top, just use the hot air module or use someone elses hot air unit you might already have. Or maybe infrared for certain things, hot air for others, you know? If the preheater isn't hooked to the top heating unit, we could switch things out. It could take up less room too because you could store it in different configurations when you're not using it. Stuff like that.