QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
Not so sure I agree here. The VinHiMin and VinLoMax values will be purely dependant on the family (HC, HCT, LS, etc) not the part itself.
Sorry. You're right. I was a bit over-ethusiastic saying "any" 05. I really meant 7405, 74L05 or 74LS05, and possibly others.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
That's pretty good. I presume that chip is a 74LS05 (low-speed CMOS hex inverter w/ open-collector outputs, correct? It should work for all designs, because the LS VinLo is only 2V.
Yes, the chips I have are LS05s, but according to the data sheet I have the plain 05 and the L05 both have 2V VinLo.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
However, you probably don't need to bother with connecting unused inputs.
Agreed. I only did so because I had tied the outputs high through the same resistor I was using for the first LDOUT/TRAYIN stage so I needed to ensure those outputs wouldn't drag the "communal" output low.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
They recommend it, but for a design like this, it's simpler without. Either way, you certainly don't need to bother with connecting the unused output pins.
OK. Thanks for confirmation on that. It will certainly simplify things if we can just basically ignore the three unused inverters.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
I'd say put this in a tutorial and ship out.
If anyone else wants to do so I will not object. Personally I'm not ready to do that yet, and I may not do it even when I am ready. Even these postings are a more of a drain on my time than I can really afford.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
The only caveat being that I can see people immediately ignoring the LS part and buying HC parts, innundating the board with "why does my drive not work?" questions.
Indeed. I'm still not convinced that this is the "best" way to go anyway. I'm still quite attracted to the op-amp approach if I can get it working more simply.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
Do we really worry about $2-$3 ? Most people will probably spend more on gasolline or shipping just to get these chips. If you order in quantity, it's even much cheaper.
I worry about it because I will probably be selling modified drives and "in business, every dollar counts". However, in the case of 324s vs 358s it doesn't matter if the 358s are more expensive per op-amp if you wouldn't be using half the 324's op-amps anyway.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
Either way, I'm bettng both 324 and 358 will work just fine. The 324 is available in most hobby-type electronic shop, so I presume availability would be good. Not sure how important sizing is, however. How much room do we have in the drive casing? Seems like there should be a fair bit of empty room, no?
There is quite a bit of empty space at any given moment, but a lot of it is clearance for things going up and down or in and out. The other thing of course is that ideally you want the space to be near where the wiring connects to the circuit board so that you don't need to have wires trailing all over the place. Even disregarding all that, I would think it's probably easier to just sort of "jam it in somewhere" if it's half the size.

QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
Opamps actually are internally "slowed down" so the device remains stable even at higher frequencies. They are otherwise almost identical to a comparator, which means the comparators will switch faster (hi to lo, etc) and is sometimes important for a digital system. I'm betting the 324 should be fast enough here, and certainly smipler.
Ah-ha. Thanks for that. I certainly wouldn't think speed is a big issue here either.
QUOTE(HunTerror @ Mar 7 2005, 01:34 PM)
What about just using a 74LS04 (74HCT04)? No pullups, etc.
My original reason for rejecting them was that the datasheet I have lists the VoutHi as 3.4V at Vcc=5V. I'm think that we're dealing with CMOS inputs that want 4V or thereabouts.
I'll PM you about the firmware flasher momentarily (couldn't quote that bit of your post. Dunno why. Too many quotes, maybe...?).
This post has been edited by wenid: Mar 7 2005, 06:51 AM