Print PDF
Favorite
Email
I am working on a project ( Instructable soon to be published) which required the Arduino controller to be powered down once a program had been run and restarted at the push of a button. The Pololu Pushbutton Power Switch fit my needs perfectly. This device was so easy to use and has so much potential in other projects I thought I would do a quick write-up in the hopes of helping others.
I use the Arduino as an example, but many other configurations are possible.
I use the Arduino as an example, but many other configurations are possible.
Remove these ads by
Signing UpStep 1The pinouts
I am using the low voltage version which can handle 2.5-7 volts. The standard version can handle 4.5-20 volts. A small switch is provided, but any momentary on switch can be used.
The pinouts of the switch are pretty straight forward. There are two pins for Voltage In (VIN), two for Voltage Out (VOUT), four for ground (GND) and one pin marked OFF.
The pinouts of the switch are pretty straight forward. There are two pins for Voltage In (VIN), two for Voltage Out (VOUT), four for ground (GND) and one pin marked OFF.
| « Previous Step | Download PDFView All Steps | Next Step » |
The switch is an electronic switch that will turn on and off power to ANY project or product you wish to use it on. It gives you a SOFT SWITCH option, like all the new electronics use, instead of a manual HARD switch such as a toggle or slide switch.
In some cases someone may not want a big toggle switch or slide switch sticking out, ao you con just have a flush mount momentary push button to use as your switch(Just like all the fancy new electronics gadgets you buy now a days).
The option of the OFF input on the switch give you a way to use an alternative method to turn off your project. In the case above, youevolve is using a pin on the micro controller to turn the entire project off. This will save more power than just letting the micro-processor go to sleep.
Any help appreciated.
It does not monitor voltage and turn off at a certain voltage.
The meaning of the low voltage switch is that it is meant to be used in a circuit that uses between 2.5 volts and 7 volts. The standard version of this switch is for use in circuits that require between 4.5 volts and 20 volts.
Hope this clears things up. Sorry it's not what you were looking for.
It just doesn't say how to do this or adjust this low voltage condition? I thought you guys might know? I've already written to Pololu about this but go no reply.
I basically wanted to the LV version to turn itself off at 3V because I'm using LiFePO4 3.3V batteries & they should not be discharged below 2.7V or they will be damaged. So I wondered how the LVC is implemented & if it could be changed by changing a resistor on board? Does anyone have the full schematic of this switch?
http://www.batteryspace.com/pcmforlifepo4packs.aspx
They have many different modules depending on your voltage needs and other specs. These may be able to be used in conjunction with the Polulu power switch.
I hope this helps a little.
Dan
I know about these PCMs but don't need anything that complex - I simply need an LVC. I thought this switch had it? Is the full schematic available so I could evaluate what changes might be need on the pcb for it to work in the way I require?
Dan
Thanks, John
Dan
Thanks to Pololu for the great products. I especially love those tiny boost regulators. The smallest version I made with through hole stuff and a MAX1771 was about the size of an Arduino mini, and that's using a home etched board. My early breadboard modes were almost credit card size. They have ones about half the size of a postage stamp. Good stuff!
Say you have a push button that you want to use to Turn on the arduino, and then let it time out after a little bit. Would you simply write in a method that reads if a button is pushed, to switch pin 7 to low?
i gather that the purpose is to give the arduino a chance to shutdown (so it's a shutdown button not a power button...sort of like if you press the power button on your PC..) but it would be nifty to include some info as to how the polulo does this etc..
This could be used in something like a museum display where the user presses a button to see a display and then can walk away without manually shutting the display down.
The Pololu switch does actually shut the microcontroller down totally, greatly saving battery power.
the press initiates the "code" then tells it to stop at a predefined time period...
how do the guts of the switch itself help with this? is it because it's a multi part switch?...like pressing the switch pulls one of the pins high...the arduino detects that and does it's do, waits it's wait, and then sends an "off" signal to the off pin on the pololu (who came up with that name) which in turn tells the switch to kill power?
http://www.pololu.com/catalog/product/751
You have the basic idea. The stop trigger could be a programmed timer or any other condition. It is all in how you want to set up your program.
IMO the more info (and explanation) you can get into the ible itself...the better it's going to be
Also, many microcontrollers have sleep functions (at least I know avr does) where it takes practically no current (It's on the scale of a few micro amps, that is millionths of an amp).
I would like to note that the Pololu Power Switch does not require a microcontroller, which allows it to work over a large range of voltages and gives you the ability to turn off your project even when the firmware is malfunctioning. Also, the < 0.01 uA off current of this switch can easily be several hundred times better than what you get with a sleep function, giving you that much more battery life!
-Paul