4011 vs 7400 ICs
Buck Childers
4011 and 7400 are both described as Quad NAND chips. What's the
difference? Can a 7400 be used instead of a 4011 in a PWM circuit for
speed control of a small DC motor?
Thanks,
-Buck
Stephen Cranage
Difference is the logic family. 4XXX is CMOS, and 74XX is TTL. CMOS runs
on a wide range of supply voltage, whereas 7400 is strickly 5V. Also many
other differences I won't go into fully, such as high input impedance of
CMOS relative to TTL, lower speed, much lower power, etc, but the supply
voltage alone usually will stop you from doing a pin for pin replacement
without modification to an existing circuit.
RonOuul
In article <33D363...@ldpd.gtd.eds.com>, Buck Childers
<bchi...@ldpd.gtd.eds.com> writes:
>4011 and 7400 are both described as Quad NAND chips. What's the
>difference? Can a 7400 be used instead of a 4011 in a PWM circuit for
>speed control of a small DC motor?
A 555 timer is designed for this type of aplication neather the 4011 or
the 7400 are. Why not use what works best.
Ron Woodward, P.E. Yorktown, VA
Hm Ron...@aol.com Wk usca...@ibmmail.com
http://members.aol.com/RonOuul/index.html (Ron's Robot Lab)
When the machine knows enough to ask "Whats in it for me?" then its inteligent!
Richard Steven Walz
In article <33D363...@ldpd.gtd.eds.com>,
Buck Childers <bchi...@ldpd.gtd.eds.com> wrote:
>4011 and 7400 are both described as Quad NAND chips. What's the
>difference? Can a 7400 be used instead of a 4011 in a PWM circuit for
>speed control of a small DC motor?
>
>-Buck
-----------------------------
Of course. The considerations are what it controls and what are the
required currents and voltages. You need to be QUITE specific to discern
which might be better, or if it's a personal choice. The two families are
different, but they do the very same logic jobs! You DO think an old PC
could handle PWM for a small DC motor, don't you? They're made with TTL.
Or is this motor so small that the 4011 could run it by itself? TTL won't
source enough current for that, which is CMOS's forte. But CMOS is slower!
It all depends on the WHOLE problem. If you used a transistor controlled by
the 7400, or better, a 74LS00, then it could drive enough juice through
your motor to roast it!! With transistor amplification, either family can
do the same!!
-Steve
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Buck Childers
RonOuul wrote:
>
<snip>
> >speed control of a small DC motor?
>
> the 7400 are. Why not use what works best.
Thanks Ron,
I would love to. I've got some 555 ICs handy, I just haven't found a
simple circuit schematic to do it. Can you provide one or point to a
resource?
btw - here's the application. Maybe I'm up the wrong tree anyway.
I'm building a scooterbot similar to the one found in Robot Builders
Bonanza. I pulled motor/gear assemblies out of a scrapped RC car called
the Ricochet. Each drive wheel was motored with independed forward and
reverse. It runs on a rechargable 9.6 NiCd bat pack. I built H-bridges
using TIP31/32s to drive each motor. The problem is that it's just too
fast. I thought I could extend the battery charge and avoid regearing
by adding a simple PWM speed control. I started with the speed control
listed in the Bonanza book (two gates of the 4011, a couple of resistors
and a capictor). This doesn't seem to work well. Speed drops but only
by a bit and there is a high pitched chirping noise. The 4011 Vcc as
well as the High 'on' input are both comming directly from the 9.6v bat
pack.
Eventually I want to make this scooterbot line following, then computer
controlled, then add an arm, then ...
Thanks for helping out this newbie,
-Buck
Bill Fry
I believe the 4xxx parts are CMOS whereas the 74xx parts are TTL.
Each (CMOS/TTL) part that has an equivalent in the other family has the
same basic functionality. What differs are such things as (various
kinds of) tolerances, voltage range, speed/latency, current draw,
fan-out, etc.
As for substituting a 4011 for a 7400 inside a [frequency-based] circuit
... I'm not sure.
I suppose it depends on the voltage range of the circuit or system,
current draw of other components (mainly the motor), etc. There are a
lot of factors that go into considering which part to use. I hesitate
to say "yes" without knowing more of your actual application.
Buck Childers wrote:
> 4011 and 7400 are both described as Quad NAND chips. What's the
> difference? Can a 7400 be used instead of a 4011 in a PWM circuit for
>
> speed control of a small DC motor?
>
> Thanks,
> -Buck
John E. Perry
Bill Fry wrote:
>
> I believe the 4xxx parts are CMOS whereas the 74xx parts are TTL.
> Each (CMOS/TTL) part that has an equivalent in the other family has the
> same basic functionality. What differs are such things as (various
> kinds of) tolerances, voltage range, speed/latency, current draw,
> fan-out, etc.
>
There are two major differences between the 4xxx series and the 74xx
series. First, the pinout. I haven't seen anyone point this out yet,
so I mention it in case it isn't obvious to you. Second, the old
original 4xxx series had a very wide range of Vcc from ~5 to ~15V. The
74xx series requires 5V +- 5%. I notice you're using your 4xxx's from a
9.6V battery, so you can't simply plug in any 74xx, even if they had the
same pinout -- which they emphatically don't.
In any case, from your description, changing the family won't solve your
problem. If I understand your description correctly, you're using the
4011 as an inverter oscillator and varying the bias to change duty
cycle, which can only be done practically in cmos. You could try the
cmos 74cxx, 74hcxx, etc, but I think you have a circuit problem,
entirely aside from the poor controllability of that kind of control
circuit.
The 555-type suggestion is a good one; there are also several ic's
dedicated to well-controlled pwm generation in the market, though I
can't think of any examples off the top of my head.
john perry
embedded electronics
jpe...@norfolk.infi.net (ignore the return address:-)