74hc595 does not work .

My 74hc595 only sink current but does not source current. when i set a one of the output pins low (for example pin 2) its sinks current, but when i set it high it doesn't sink current or source current. also i have another question, what do they mean when they say "3-state output register". pls help.

Page 6 of the datasheet says IOH = –20 μA
and IOL = 20 μA

so what EXACTLY are you trying to drive with it ? (hopefully not a led )

[u]This datasheet[/u] actually shows up to 6 or 7mA either way, depending on Vcc and what you need as output-high and output-low voltages.

also i have another question, what do they mean when they say "3-state output register".

It's an option you don't have to use. When the Output Enable pin is high the outputs are "disabled" to a high-impedance state. That might be your problem!

In general, you can't "short" two output pins together. For example, you can't connect the outputs from two Arduino's to two different things at the same time* because if one writes high and one writes low, they are "fighting each other" and you'll get excess current.

But with tri-state devices you can "tri-state"(disable) all but one device at a time and you can share output connections. You probably don't need this feature unless you can connecting to a shared data bus or something like that.

You can do the same thing with open-collector or open drain devices (as long as you're always writing-high from the unused devices). Open collector & open drain devices need a pull-up resistor to go-high because they are not driven high.

  • You can if you CAREFULLY switch one of the I/O pins to input-mode.

I've tried to drive 8x8 led matrix. i have even tried to connect a 1k resistor and my multimeter in series but my multimeter shows 0.00 mA. also everyone has the same shift register as mine but mine doesn't work.

Try this tutorial.

I've tried it before. i think my shift register is broken. I've tried to control it using push buttons by pressing the clock button then the latch button.

I have never had any problem driving seven segment leds with the 74HC595. If you actually look at the schematics, the typical wiring is sinking current, NOT sourcing. I suggest you adjust your wiring accordingly by using transistors to sink the led current and using the 74hc595 to drive the transistors through a 470 ohm to 1k base resistor.

I've seen people driving leds by connecting the the anode to the shift register outputs and the cathodes to ground through a 220 ohm resistor. please give a shift register name that can source current and i will buy it from aliexpress. Thanks for helping me.

TPIC6B595, TIPC6C595, MIC5891

Digikey & Mouser has them all, on the order of 50 cents plus sales tax/shipping.

Didn't you get the answers you hoped for in your duplicate thread. Cross-posting wastes time (yours and ours), and is against forum rules.

That ShiftOut page has long-standing errors (more thn 10 years), that we can't seem to get corrected. The cap should NOT go on one of the data lines, but from VCC to ground. The circuit diagrams are correct, but the breadboard pictures are not. Leo..

Hi,

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html . Then look down to item #7 about how to post your code. It will be formatted in a scrolling window that makes it easier to read.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom... :)

Not sure what you are seeing but it should source or sink about 30mA with a package maximum of about 70mA. Check the data sheet: http://www.ti.com/lit/ds/symlink/sn74hc595.pdf

3-state output register indicates the output can be high, low or unconnected (TriState). If it is not enabled high it will not sink or source anything. I think this is your problem. I think it is floating. Good Luck, Have Fun! Gil

CrossRoads: TPIC6B595, TIPC6C595, MIC5891

Digikey & Mouser has them all, on the order of 50 cents plus sales tax/shipping.

At least the first two can only sink current, not source.

gilshultz: Not sure what you are seeing but it should source or sink about 30mA with a package maximum of about 70mA.

That's an absolute maximum for the package; the single pins can source or sink far less than that. Definitely no 30 mA per pin. The data sheet lists an absolute maximum rating of 20 mA per pin, on a quick skim I don't see the recommended maximum ratings.