# hex inverters - help with what's what in a circuit symbol?

hey, so i'm using a hex inverter for the first time in this circuit (bottom left of these 4 images):

notice the triangular images for the hex inverter. here is the datasheet for the inverter: http://focus.ti.com/lit/ds/symlink/sn74ac04.pdf

i have no idea what this component is doing here, first of all. more importantly, i don't know how to figure out what pins correspond to what part of the symbol in the circuit diagram. perhaps someone would take the time to explain these things to me?

thank you for your time nym

So you've got triangles with a 'o' one end - A high goes in the flat end, a low comes out the circle, & vise versa. My internet access is flakey at the moment, so I can't see your images, ti.com not even opening.

Note it is a hex inverter, that is to say there are six inverters in the one package, each inverter is identical. For inverter 1 - input pin 1 output pin 2 For inverter 2 - input pin 3 output pin 4 For inverter 3 - input pin 5 output pin 6

For inverter 4 - input pin 9 output pin 8 For inverter 5 - input pin 11 output pin 10 For inverter 6 - input pin 13 output pin 12

For all inverters positive supply is pin 14 and negative (ground) pin 7.

You will notice the circle on the end of the symbol is filled, if it were unfilled it would signify an open collector output. Those needs to be externally pulled high with a resistor.

The left hex is acting as an oscillator driver to “excite” the crystal oscillator. The hex on the right is acting as an impedance buffer to prevent the IR sensor circuit unduly loading the crystal oscillator. From the data sheet the diagram clearly shows the “A” is the input to the hex circuit and the “Y” is the output. 1A and 1Y are the respective inputs and outputs for hex unit number 1, 2A and 2Y for hex unit number 2 etc. It matters not which hex units you use in the circuit. Simply pick a couple and leave the others redundant. It’s usual to ground the input ports of the unused units to prevent any possibility of them oscillating.

Wish I could see the picture! Thunderstorm south of here, tornado watch & tornado warning, gonna be an exciting evening!

awesome, again. arduino forum to the rescue tonight. enjoy your storm! clear and sunny here in san francisco. we could use the rain.

I suppose I don't speak for the entire Boston area, but I'd personally gladly ship you some of our rain. We had a very rainy spring, and our reservoirs are pretty full (for which I'm grateful -- they were low over the winter). But tonight's weather, which pales in comparison to other recent extreme weather, I wouldn't wish on anyone. I seem to be between bands of storms.

7404 is not open collector by the way. That 7404 based oscillator was the very first circuit I ever built by myself.

Also, I moved from Marlboro to Atlanta and I would love it if you could ship some rain this way.

Yeah, there ought to be an efficient way to get water from where it's abundant to where it's needed.

@pwillard, why'd you leave? Not hot & steamy enough up here in the summer for you 8) ?

Moving the water - just need to build some more pipelines.