| |
 |
|
|
Science Forum Index » Electronics - Misc Forum » trouble with logic counters
Page 1 of 1
|
| Author |
Message |
| panfilero |
 Posted: Tue Jan 02, 2007 1:05 am |
|
|
|
Guest
|
Hello, I'm trying to hook up a 74HCT163 to count from 0 to 7 then loop
and keep doing it. I'm having a lot of trouble making sense of the
data sheet on how to connect this thing. I have a 555 chip creating my
clock, it's lighting an LED right now, I took that from the positive
end of the LED and am running it into the counter. I was worried about
going straight from the 555 chip to the counter cause i've heard these
type of chips are fragile, real sensitive to too much current/voltage.
I'm powering the circuit with a 9 Volt battery, I'm splitting that in
half using a couple resistors (of equal value 10 Mohm) in series and
taking the voltage from one resisttor and using it as my high for the
counter. I've connected the pins in this way:
1 MR - high
2 CP - 555 output
3 P0 - high
4 P1 - high
5 P2 - high
6 P3 - high
7 PE - high
8 GND - ground
9 SPE - high
10 TE - high
11 Q3 - not used
12 Q2 - to a 1K resistor in series with an LED
13 Q1 - to a 1K resistor in series with an LED
14 Q0 - to a 1K resistor in series with an LED
15 TC - not used
16 Vcc - high
I can't get anything to happen, and can't tell what some of these pins
are even for. Any help with this would be greatly appreciated, thanks |
|
|
| Back to top |
|
| tersono |
| Posted: Tue Jan 02, 2007 5:06 am |
|
|
|
Guest
|
On 1 Jan 2007 21:05:29 -0800, "panfilero" <panfilero@gmail.com> wrote:
Quote: Hello, I'm trying to hook up a 74HCT163 to count from 0 to 7 then loop
and keep doing it. I'm having a lot of trouble making sense of the
data sheet on how to connect this thing. I have a 555 chip creating my
clock, it's lighting an LED right now, I took that from the positive
end of the LED and am running it into the counter. I was worried about
going straight from the 555 chip to the counter cause i've heard these
type of chips are fragile, real sensitive to too much current/voltage.
I'm powering the circuit with a 9 Volt battery, I'm splitting that in
half using a couple resistors (of equal value 10 Mohm) in series and
taking the voltage from one resisttor and using it as my high for the
counter.
Whoa- what's powered from what? Your description leaves room for
confusion.
If you're running the '163 from the junction of the two 10M, then
that's like feeding it from 4.5v- OK-
!!!!! *but with 5M in series with the supply*!!!!!
- and even if the '163 pulls only a microamp, that leaves it with no
supply volts. (Does "Thevenin" mean anything to you?)
If you've put 9v directly on the '163, you've probably broken it. (But
maybe you don't mean that).
Why not run everything from 4.5v? Your LEDs would be dimmer, but
live with that. Put 1n or 10n capacitor across the supply
Quote: I've connected the pins in this way:
1 MR - high
is master reset- active low- so you're letting it run. OK
2 CP - 555 output
clock input to '163- OK
3 P0 - high
4 P1 - high
5 P2 - high
6 P3 - high
above are parallel data inputs- don't matter for your purposes
7 PE - high
Count enable- OK
8 GND - ground
9 SPE - high
Low would force counter to state of pins 3...6- so OK
10 TE - high
Enables carry input- OK
11 Q3 - not used
12 Q2 - to a 1K resistor in series with an LED
13 Q1 - to a 1K resistor in series with an LED
14 Q0 - to a 1K resistor in series with an LED
OK
15 TC - not used
16 Vcc - high
I can't get anything to happen, and can't tell what some of these pins
are even for. Any help with this would be greatly appreciated, thanks
--
Per ardua ad nauseam |
|
|
| Back to top |
|
| CWatters |
| Posted: Wed Jan 03, 2007 6:37 am |
|
|
|
Guest
|
"panfilero" <panfilero@gmail.com> wrote in message
news:1167714329.373160.286940@48g2000cwx.googlegroups.com...
Quote: I'm splitting that in
half using a couple resistors (of equal value 10 Mohm) in series and
taking the voltage from one resisttor and using it as my high for the
counter.
That won't work...
Each output LED that is illuminated will draw a few mA in through pin 16 and
out of the relevant Q of the 74HCT163. That current would cause a large
voltage drop through the 10M resistor betwwen Pin 16 and the 19V battery.
Lets estimate the current at 2mA - the voltage drop would be 2 x 10^-3 x 10
x 10^6 or about 20,000V or at least it would if the supply voltage was
Why not power the whole circuit from a 5V source and use version of the 555
that will work from 5V power rails. If you need to make 5V from 9V then use
a three pin reglator (7805 series) and some capacitors. |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Thu Jan 08, 2009 5:29 pm
|
|