Hello,
I'm trying to teach myself electronics so I guess this counts as "self assigned homework"
I've got an SN74HCT08, Quad 2input AND gate (http://www.nxp.com/documents/data_sheet/74HC_HCT08.pdf)
It's always running "TRUE" and I don't get why: mind you this is the very first IC i've ever tried to hook up. Have read the datasheet but no doubt missing something
i.e. my LED is bright. This seems odd to me: I'm thinking perhaps "1A and 1B disconnected" somehow still triggers TRUE, whereas perhaps 1A and 1B at 1.35V (the datasheet max low voltage) would give me the desired FALSE at this point?) Given the datasheet doesn't list a minimum for "low" I would assume that disconnected is as low as you can get and would satisfy the logic?
I also routed 3.3V in to my input pins, 1A only, 1B only, as well as 1A-and-1B... still 1Y remains TRUE, LED glaring at me like it knows something I don't... stoopid smug LED! (image37)
Thanks heaps for any help you can offer
First Post Done!
- Simon
I'm trying to teach myself electronics so I guess this counts as "self assigned homework"
I've got an SN74HCT08, Quad 2input AND gate (http://www.nxp.com/documents/data_sheet/74HC_HCT08.pdf)
It's always running "TRUE" and I don't get why: mind you this is the very first IC i've ever tried to hook up. Have read the datasheet but no doubt missing something
- I've got a 5v feed to the right side of a breadboard from a Pi, and a 3.3V in to the left side (for benefit of understanding my photos below)
- I've got ground from the Pi (pin6) going to board
- I've got +5v running in to VCC pin (at top right of IC)
- I've got the GND pin connected to ground
- I've got an LED going from pin "1Y" to ground through a resistor (100R, probably a third of what i SHOULD be using I think? But destroying my Pi aside...)

I also routed 3.3V in to my input pins, 1A only, 1B only, as well as 1A-and-1B... still 1Y remains TRUE, LED glaring at me like it knows something I don't... stoopid smug LED! (image37)

Thanks heaps for any help you can offer
- Simon