Counter/ Timer

[DaveK]

I’m a baseball coach at a high school and when we use our pitching
machine our players want to hit more balls than they should. I would
like for an alarm to go off after a pre-determined amount of pitches.
The machine has an arm connected to a wheel that rotates. Each full
revolution equals one ball pitched. I would like to count each
revolution (pulse) of the wheel either by a limit switch or even a
reed switch with a magnet on the wheel. Maximum pitches would be
somewhere around 10. There is 110 vac at the machine so I can run most
any dc voltage through a transformer to run a circuit. I have played
around with the 4017 counter/divider and the 555 timer but I don’t
seem to be getting anywhere. What would be the correct type of circuit
to use for this type of application?
I’m not real experienced with electronics but I can follow a schematic
and build a circuit. I would have to have a complete schematic in
order for me to do this. I’m not sure how much time it would take to
make a schematic of this sort but any information would greatly be
appreciated.

Thank You for Your Time
Dave

 

[Shaun]

"DaveK" <piscatory@cox.net> wrote in message
news:56a619c0-4ba1-473d-83f8-d2fab2d57556@b2g2000yqi.googlegroups.com...
I’m a baseball coach at a high school and when we use our pitching
machine our players want to hit more balls than they should. I would
like for an alarm to go off after a pre-determined amount of pitches.
The machine has an arm connected to a wheel that rotates. Each full
revolution equals one ball pitched. I would like to count each
revolution (pulse) of the wheel either by a limit switch or even a
reed switch with a magnet on the wheel. Maximum pitches would be
somewhere around 10. There is 110 vac at the machine so I can run most
any dc voltage through a transformer to run a circuit. I have played
around with the 4017 counter/divider and the 555 timer but I don’t
seem to be getting anywhere. What would be the correct type of circuit
to use for this type of application?
I’m not real experienced with electronics but I can follow a schematic
and build a circuit. I would have to have a complete schematic in
order for me to do this. I’m not sure how much time it would take to
make a schematic of this sort but any information would greatly be
appreciated.

Thank You for Your Time
Dave

Hello Dave,

You could use the 555 as a "one shot" oscillator, one pulse per revolution
and the 4017 to divide down the to the right count. I've just experimented
with the 4017 and I think the Q9 output will give you a count of 10. That
output could be used to trigger another 555 as a time delay for the alarm(
time on). Then a transistor and an alarm of some sort.

Shaun

 

[John Fields]

On Tue, 24 Nov 2009 19:52:48 -0800 (PST), DaveK <piscatory@cox.net>
wrote:

I’m a baseball coach at a high school and when we use our pitching
machine our players want to hit more balls than they should. I would
like for an alarm to go off after a pre-determined amount of pitches.
The machine has an arm connected to a wheel that rotates. Each full
revolution equals one ball pitched. I would like to count each
revolution (pulse) of the wheel either by a limit switch or even a
reed switch with a magnet on the wheel. Maximum pitches would be
somewhere around 10. There is 110 vac at the machine so I can run most
any dc voltage through a transformer to run a circuit. I have played
around with the 4017 counter/divider and the 555 timer but I don’t
seem to be getting anywhere. What would be the correct type of circuit
to use for this type of application?

---
Basically, you'd use the 555 to debounce the switch and generate a clock
for the counter, once per revolution of the wheel, and then sound the
alarm when the counter got to nine.

After that you have a choice as to what to do about resetting the alarm:

On the one hand you could have it stay on until you reset it by hand,
and on the other you could just let the counter overflow to zero when
the next pitch is thrown. That way the old batter would know when his
turn was over and when the new batter took his place the alarm would go
off when he was pitched to the first time.

The manual reset would be nice in order initialize everything on
power-up or if things got out of sync somehow.
---

I’m not real experienced with electronics but I can follow a schematic
and build a circuit. I would have to have a complete schematic in
order for me to do this. I’m not sure how much time it would take to
make a schematic of this sort but any information would greatly be
appreciated.

---
Here's the schematic; view it using Courier or any non-proportional
font.

Vcc>-+---------+-----+----------+--------+---+-------------+
| | | | | | R6|
|R1 R2| R3| 8| R4| | [10K]
[10K] [10K] [1M] +---+---+ [10K] | C3 |
| | Rt| |_ Vcc _| | [100nF] +---+
+-[100nF]-+-----|---2-O|T R|O-4-+ | | |
| C1 | | | | | R5 | C
+ +---6--|TH 7555| +---|-[100K]--|-B 2N3904
| | |_ | | | | E Q1
| O S1 +---7-O|D OUT|O-3-|---|-+ | |
| O C2| | GND | | OS2 | | | |
| [0.1ľF] +---+---+ | O | | | |
| Ct| 1|U1 | | | | |
GND>-+---------------+----------+--------+---+-|-------|---+
| |
+---------------+ | Vcc
| +---------------------+ |+
| | ALARM]
| | |
| | +------+ C
| +-15-|R Q9|-11--[1K]--B 2N4401
| | | E Q2
+---14-|> | |
| 4017| GND
GND--13-|INH |
+------+
U2

Here's how it works:

When power is turned on, S2 (a SPST NO pushbutton switch) is momentarily
made, resetting U1 by pulling U1-4 low, and pulling the base of Q1 low
through R5. This low turns Q1 off, pulling its collector up to Vcc
through R6. The high on the collector of Q1 then pulls U2-15 high,
resetting the counter.

When S2 is released, U1 and U2 will be enabled but nothing will happen
until S1, a momentary SPST switch, is actuated by the wheel of the
pitching machine.

When S1 is made, the junction of R1C1 will be pulled down to GND, which
will cause the junction of R2C1 to go low momentarily, pulling U1-2 low
and triggering U1.

Triggering U1 causes its output to go high momentarily, and the leading
edge of that pulse is used to clock U2, a Johnson counter with 10
mutually exclusive outputs.

When the counter is reset, its "0" output will go high and stay high
until it's clocked, at which point the "0" output will go low and the
"1" output will go high.

As each new clock pulse appears, the counter increments, and when it
gets to "9", U2-11 will go high, turning Q2 on. When that happens the
negative side of the alarm will be connected to GND through Q2 and the
alarm will, effectively, be connected across the supply, causing it to
sound continuously until either S2 is pressed or S1 is actuated by the
wheel.

In either case the result will be the same in that U2 will be reset, U1
having already reset itself by timing out.

For the alarm I'd use something like a Sonalert with an internal
oscillator:

http://www.mallory-sonalert.com/

Because they can be had quite loud, aren't that expensive, and can be
had through distribution. Digi-Key, Mouser, Newark... Everybody, just
about.

Finally, for the supply, if you're using CD4XXX logic you can run it up
to 18V. Personally, I'd use 12V to get the maximum out of the alarm.

JF