12 replies to this topic

[MarkWill]

I just ordered my Netduino - and can't wait!!! Is this a reasonable place to post a question along the lines of "I need some hardware that will..."? I have a quirky little project in mind that would really interest me (because I'd use it!). Part of it's design would be a couple of switches that would be controlled with my thumbs, while holding the handle of a rowing machine (mounted on the handle between my hands as I row). The idea is that these two switches would be clickable with my thumbs while rowing and send a message to a Netduino project I have in mind. All the logic for the interpretation and actions for the switch clicks would be handled by the Netduino. However, there are challenges with the switches I would need. They would need to be momentary, extremely flat (stick on to the rowing handle), not sensitive to regular jarring (my rowing!), no more than - say - an inch wide and very light (since I'd be rowing and I don't want to be carrying extra weight on the handle). So, the switches would be a key part of the design - and I have no idea where to look. Anyone have any thoughts? Thanks in advance. Mark

[Fred]

Rememeber those "clicky" flat panels where the buttons were domed (almost like very low profile bubblewrap)? I haven't desribed it well but I'm sure you know what I mean. I think you need something like that. As for where to find them (or even what to google for)...

[Eric Burdo]

Sometimes they are referred to as "momentary contact switches". I think if you contact places like Mouser.com and Jameco.com (and probably Sparkfun.com) you can check out their online/offline catalogs. Being that flat... you might get stuck with a surface mount... which is harder soldering.

[Patrick]

What about two piezo vibration sensors? You could probably only accept large voltage increases as presses to minimize false positives from vibration... http://www.sparkfun....roducts_id=9196

[MarkWill]

Rememeber those "clicky" flat panels where the buttons were domed (almost like very low profile bubblewrap)? I haven't desribed it well but I'm sure you know what I mean. I think you need something like that. As for where to find them (or even what to google for)...

Yep, that's exactly what I mean. And, like you, I also struggled for a search term :-)

Thanks.

Mark

[MarkWill]

Sometimes they are referred to as "momentary contact switches".

I think if you contact places like Mouser.com and Jameco.com (and probably Sparkfun.com) you can check out their online/offline catalogs.

Being that flat... you might get stuck with a surface mount... which is harder soldering.

You raise another issue I forgot - the surface on which they are mounted is not flat :-) It's basically a cylinder.

Mark

[CW2]

You raise another issue I forgot - the surface on which they are mounted is not flat :-) It's basically a cylinder.

Can you drill a radial hole into it?

[CW2]

You raise another issue I forgot

Waterproof?

[MarkWill]

Waterproof?

Waterproof would be good (persperation) and also I would prefer some other way to securely mount the switch without drilling.

Thanks.

Mark

[MarkWill]

I'm very much the newbie in town - but this looks promising. http://www.ladyada.n...ensors/fsr.html Mark

[Frank]

If you're in an area with a recycling center, go pick up some of the kids toys and electronic games. Almost everything for kids these days has buttons that make things talk, or move, or jump, etc. And being designed for kids they are often clean simple not much bothered by water, slime, drool, etc. I often bring home a 'toy' from the recycle center, or dump, or transfer station. They are a constant supply of gears, motors, LEDs, buzzers, things that talk, mechanical movements. And the upside is the Grandkids are well supplied with 'things' they can play with, that usually work well , and cost nothing. I'm sitting here looking at a couple of rubber coated, thin, membrane switches on an old Hasbro talking dog. I'm sure they were designed with kids in mind, and rough usage!

[jcarter]

I would have said force sensors would be the obvious choice here.. as they are basically paper thin, and weight nothing. Just calibrate them to fire over a certain 'pressure' of stroke. See: http://www.google.ch... resistor (FSR)

[MarkWill]

I would have said force sensors would be the obvious choice here.. as they are basically paper thin, and weight nothing. Just calibrate them to fire over a certain 'pressure' of stroke.

See: http://www.google.ch... resistor (FSR)

Thank you. Yes, that looks like a reasonable approach to me. What isn't so clear to me is where the logic resides to define a "keypress". This question will expose my lack of experience in this area (and, as I write, my lack of Netduino, which should be here by the end of the week!).

As I understand, the force resistor will basically return a value (indirectly, at least). I presumably need to define the minimum force (resistance) to start the "click" and the maximum for when it ends. Is this the sort of logic I define myself in my own code (and what sort of event do I use to identify when the method I wrote should be checked)? Or can I define some sort of event handler that detects when the resistance changes (does it change by tiny amounts without any actual pressing or will it be at a "known" resistance unless someone actually presses)?

Or - he said wishfully - does the .Net Framework provide some sort of abstraction to all this so that I can identify the resister as my "key" and just receive key-up and key-down like events?

Thanks again.

Mark