Created Tue, 11 Oct 2011 11:42:45 +0000 by walnuts
Tue, 11 Oct 2011 11:42:45 +0000
I've read in several threads that it is possible to set pins to Open Drains and get 5V outputs from them but I'm just not understanding how to do this and have not been able to piece the info together successfully. I'm using a Max32 currently but will be switching to a UNO32 for the finished project that I'm working on.
I want to use pin 9 to control either directly power a Piezo buzzer (http://www.radioshack.com/product/index.jsp?productId=2062405) which I is rated at operating on 6-12V but will run on as little as 3.6V and easilly from the 5V supply pins on the Max32 or indirectly through a micro relay (http://www.radioshack.com/product/index.jsp?productId=2062480) but I think the relay is going to require far too much amperage to run directly from the board.
If this just isn't going to be possible at all because I'm looking for too much power from the board, can someone please suggest a better route? I really need "an idiot's guide" version here folks.
Tue, 11 Oct 2011 12:16:59 +0000
Simplest way to do it is bung a resistor (1k ish, haven't done the sums) from the pin to an NPN switching transistor (2N3904, 2N2222 etc) and wire the piezo from a static power supply to the transistor.
Fri, 06 Apr 2012 07:43:45 +0000
I suggest using one or more SN74ABT244 to raise your output signal level to 5V and to drive higher currents. They can be powered from the 5V regulator or USB power provided you don't draw more current from the outputs than the USB can provide. The buffers will also protect your processor from short circuits.
I have several SN74ABT244s mounted on a separate PC card. I could cut my jumper wires in half if I mount the buffers on a piggyback card that plugs into the chipKit sockets. Pins would pass through the piggyback card to extend the chipKit sockets for input connections. Additional pins or sockets would provide 5V outputs from the buffers. The piggyback board should also provide power pins with several (8) ground pins.
I have an immediate use for such a piggyback card. If anyone have the capability to manufacture PC cards, please contact me.
Wed, 11 Apr 2012 15:22:18 +0000
If only driving buzzer, still can use 3V with transistor switching. If connect to IC operate in 5V, then 3V is still considering HIGH state for that IC. If really2 needs 5V output, maybe can use opto-coupler.
Wed, 11 Apr 2012 19:01:08 +0000
Ive been usind a 74HTC04 inverter seems to work OK .