is there an octal buffer that is generally used to buffer the outputs of a pic. all of the ones i see are tristate. i just need something to supply a little more current. a darlington array mabey? but they are a bit pricey
is there an octal buffer that is generally used to buffer the outputs of a pic. all of the ones i see are tristate. i just need something to supply a little more current. a darlington array mabey? but they are a bit pricey
is there an octal buffer that is generally used to buffer the outputs of a pic. all of the ones i see are tristate. i just need something to supply a little more current. a darlington array mabey? but they are a bit pricey
The PIC i/o are connected to the input pins (left hand side) and I connected LEDs to the outputs.
The 220k resistor network and 220k resistor (could not buy a longer RN as the shop was out of stock) is to pull the inputs low when some or all of the PIC i/o pins are defined as inputs.
The 74HC573 is a tri state, but I've disabled the tri state to make it a straight buffer. See the data sheet for the 74HC573.
It all depends how bright you want the LED's, a PIC could easily do it without a buffer - or you could simply feed the LED from collector of the TIP140, why have two buffers?.
the darlingtons are going to be driven by a fairly long wire and the leds are going to be on the board with the pic. which is another reason i want something between the pic and the darlingtons because if the wire got shortedi don't want to desrtoy the pic
Nigel's right, I don't think I've ever managed to kill a PIC I/O, even if shorted to ground when it was driven high - you could still kill them by driving them with some high-voltage external source or something of course...
I suppose... but bear in mind that the 25mA limit is per pin - and that usually the next restriction on top of that is a combined 100mA per PORT, and usually 200-300mA for the whole chip.
Not that I'm suggesting it's a good idea to push the limits, but you can probably get away with more than you might think - LED's with proper current limiting resistors are a piece of cake, though running bipolar power transistors might indeed make the buffers worthwhile depending on what you're switching.