I've been going through a lot of component vendors and articles trying to find the right type of button/switch. What I'm looking for is a button that acts as a toggle switch, so one press for ON and then press again for OFF. I can't find what the technical name or just the name of these types of buttons/switches or if they are even easy/cheap to find. Does anyone know what I'm looking for?
Mostly buttons have sets of 3 contacts (1, 2, 3, etc. sets depending on switch), where in each set two of contacts are connected almost at all times, so you can make both - switch or on off button. Sets are isolated between each other.
Also there are latching and non latching switches - those staying put and those switching only while you hold them.
Cheapest are what's called "tact switches" or "tact push-buttons". Those are meant for PCB soldering, low currents/voltages, but are much smaller and more convenient for small devices.
You haven't mentioned how you want to use the switch.
Most toggle switches are more aimed at higher power usage and panel mounting.
If it's just a little button you are after that will toggle on/off you would probably be best off using a cheap momentary push button and doing the toggling in software - that is what most designers do - because the little push buttons are so much cheaper than toggle switches.
It's called a "Push-On/Push-off" switch. ([u]example[/u]). A pushbutton that does NOT stay-on when the button is released is called a "momentary" switch.
majenko:
You haven't mentioned how you want to use the switch.
Yeah sorry, I had originally then it bounced my post so I let it out the second time. This idea is I want to cut power to either the micro-controller (Some sort of Atmel) or to cut the supply to a set of LEDs to conserve power when not in use. Because of what it is, I would rather it be a button because it would protrude a little less than most of the toggle switches I found. Also I just want the button press sensation.
majenko:
you would probably be best off using a cheap momentary push button and doing the toggling in software
I could but I was thinking I could just cut the power to the micro-controller, saving even more power. I have a number of the momentary tact switches right now but they aren't what I want to do.
So I found two on EBay that I like but they aren't very well described. The first one, http://www.ebay.com/itm/10pcs-Self-Lock-ON-OFF-lock-Push-Switch-8x8mm-8-8mm-/130704614546?pt=LH_DefaultDomain_0&hash=item1e6e9a2492, looks like the right kind but doesn't have a cap on top. The second one, http://www.ebay.com/itm/1pcs-Tact-Switches-3X6X5mm-black-press-key-high-quanlity-/261035650123?pt=LH_DefaultDomain_0&hash=item3cc6efec4b, is nice and small but I can't tell what kind it is. I've also looked at places like Digikey and they have an overwhelming number of styles and varieties and I don't really know what I need.
What you want then is a latching power circuit:
Oh that actually looks pretty slick. Unfortunately I am not well versed in electronics so I'm not entirely clear on what MOSFETs and Transistors do. Though they look like very basic logic gates if I understand things right. I will definitely look into trying this out.
One problem I see with it though is it might be a bit big for some small projects I have in mind, like the Firefly Jar project I want to try.
paultyoung:
majenko:
you would probably be best off using a cheap momentary push button and doing the toggling in softwareI could but I was thinking I could just cut the power to the micro-controller, saving even more power. I have a number of the momentary tact switches right now but they aren't what I want to do.
Is power an overriding concern? It may make sense to code it the simple way, and then measure the power usage, rather than jumping in and going for the more complex solution immediately. Perhaps using sleep and interrupts instead of cutting the power completely. In the software world, we often times call worrying about this ahead of time, premature optimization. Sometimes it is the overriding concern, and sometimes not.
On a previous query of mine about how many batteries to plan for, Nick Gammon give a link that discusses the many ways to reduce power usage on Aduinos: Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors
However, it occurs to me that if you going to cut power to the Arduino, you have non-volatile memory (EEPROM) that you can write some amount of state to (like the button state). In recent machines you have from 512 bytes (Lilypad) to 4KB (Mega).
Oh wow, I was not aware of the options the ATMegas had for power savings in the Arduino environment.