Yes. The "outputs" of the shift register act just like your transistor - they are "off" so then are high impedance (open circuit), or "on" and connected to ground. You need power from the 5V rail to turn your transistor on, and when you turn on the output to the shift register it connects the base of your transistor to ground, turning it off.
Ok, so most registers actually output current while mine "sink"s the current (inputs the current per-say). Is this correct?I am using this all to control an LED array. I am using the registers to control 25 columns and 15 rows. The plan is to sink 1 row at a time and make the columns provide the power so that each LED has it's own power supply, giving maximum brightness. I am using the transistors to switch on-off the power to the columns, thus giving total control.Maybe it makes more sense to get simpler output-current registers for the columns while using the sink-current registers for the rows? This would make the transistors easier to use (if I would even still need them, depends on how many LEDs I am trying to power I suppose). Is this a correct thought process?
If you are going to have lots of LEDs connected from one output of the 595 and have them illuminated *at the same time* then you will need a transistor, but as it's a "high side" switch, make it a PNP, not an NPN.
Quote from: majenko on Mar 04, 2013, 12:53 amIf you are going to have lots of LEDs connected from one output of the 595 and have them illuminated *at the same time* then you will need a transistor, but as it's a "high side" switch, make it a PNP, not an NPN.Why would I use a PNP WITH THE 595? Since the 595 would push the current, wouldn't I use a NPN transistor to control 5V flowing to each column (while using my current shift registers to sink the rows when needed)?Basically, couldn't I use the 595 ouput pins as the switch on the NPN transistor to unleash the 5V when the register pin is turned HIGH?
I am trying to learn to use the TPIC6B595N shift register http://www.adafruit.com/datasheets/tpic6b595.pdf but I am having a strange problem. The register only works every now and then and very often it works only when my hand is nearby.
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