Maker Pro
Maker Pro

basic elapsed seconds counter

Hi,

I need to build a simple timer which simply counts elapsed time in
seconds as soon as current is turned on, then turns off and resets
when the power is disconnected. Or perhaps resets then begins counting
elapsed seconds, then shuts off when the power is disconnected. I
would like to display the seconds on an LCD or LED screen about the
size of a spoon.

I have no experience with electronics but I am keen to learn!
Hopefully this will be the start of many gadgets...

I really appreciate your help. Thanks!!!

-Ben
 
S

Steve

Jan 1, 1970
0
Hi,

I need to build a simple timer which simply counts elapsed time in
seconds as soon as current is turned on, then turns off and resets
when the power is disconnected. Or perhaps resets then begins counting
elapsed seconds, then shuts off when the power is disconnected. I
would like to display the seconds on an LCD or LED screen about the
size of a spoon.

I have no experience with electronics but I am keen to learn!
Hopefully this will be the start of many gadgets...

I really appreciate your help. Thanks!!!

-Ben

What sort of accuracy do you need and how long will the timed period be?
(In other words, do you need "watch" accuracy, or within a couple of
percent, and how many digits will be needed to display the timed period?)

The timing is relatively easy, depending on accuracy and the length of
the timed period, but the display will take a bit more work.

For an LCD display, you would need a micro-controller, along with
programming skills, a compiler and a programmer and, of course, the other
hardware such as resistors, capacitors, diodes etc. Programmers and
compilers can cost a fair bit. Then you'd need to spend a bit of time
working up to the level you require. This method would provide the best
results, both in timing and quality of display, but is by far the most
expensive, especially if this is a small project.

LED displays are simpler, but need a few more chips for counting,
decoding and LED display segment driving, dependent on the number of digits.
One thing to consider is whether the unit will be used in relative darkness
or daylight. LEDs are best for darker settings and LCDs are more suited to
lighter environments.

A bit more info would help.
... Steve
 
    What sort of accuracy do you need and how long will the timed period be?
(In other words, do you need "watch" accuracy, or within a couple of
percent, and how many digits will be needed to display the timed period?)

    The timing is relatively easy, depending on accuracy and the length of
the timed period, but the display will take a bit more work.

    For an LCD display, you would need a micro-controller, along with
programming skills, a compiler and a programmer and, of course, the other
hardware such as resistors, capacitors, diodes etc. Programmers and
compilers can cost a fair bit. Then you'd need to spend a bit of time
working up to the level you require. This method would provide the best
results, both in timing and quality of display, but is by far the most
expensive, especially if this is a small project.

    LED displays are simpler, but need a few more chips for counting,
decoding and LED display segment driving, dependent on the number of digits.
One thing to consider is whether the unit will be used in relative darkness
or daylight. LEDs are best for darker settings and LCDs are more suited to
lighter environments.

    A bit more info would help.
    ... Steve

Thanks for the reply Steve,
A bit more info...
The accuracy is not an issue for me so long as it is 'fairly'
accurate. The only thing I can liken it to is when you step out a
distance- "right, that's 20 metres give or take a couple.". A maximum
time to count to would be 99 seconds. I have read a little about the
555 timer so I think that's my guy, but as for how I can use it for
this application, I'm stumped.

I also like the suggestion for a couple of segment LCD's to display
it. I hope this is enough info to get me started. Thanks again!
 
T

Tom2000

Jan 1, 1970
0
Thanks for the reply Steve,
A bit more info...
The accuracy is not an issue for me so long as it is 'fairly'
accurate. The only thing I can liken it to is when you step out a
distance- "right, that's 20 metres give or take a couple.". A maximum
time to count to would be 99 seconds. I have read a little about the
555 timer so I think that's my guy, but as for how I can use it for
this application, I'm stumped.

I also like the suggestion for a couple of segment LCD's to display
it. I hope this is enough info to get me started. Thanks again!

I just had a wacko thought. Go to your nearest drugstore, Radio
Shack, or whatever, and pick up a cheap stopwatch built into a fairly
large case.

Build yourself a little "button pusher" -- maybe a reed relay circuit
-- driven when you want to start and stop the timing. Perform a
little microsurgery on the stopwatch to solder your button pusher
across the stopwatch's start/stop button.

Voila!

Tom
 
J

John Fields

Jan 1, 1970
0
Thanks for the reply Steve,
A bit more info...
The accuracy is not an issue for me so long as it is 'fairly'
accurate. The only thing I can liken it to is when you step out a
distance- "right, that's 20 metres give or take a couple.". A maximum
time to count to would be 99 seconds. I have read a little about the
555 timer so I think that's my guy, but as for how I can use it for
this application, I'm stumped.

I also like the suggestion for a couple of segment LCD's to display
it. I hope this is enough info to get me started. Thanks again!

---
This will work: (View in Courier)


[7555]---[4510]---[4510]
| |
[7555]-+-[4543]---[4543]
| | |
+-[7SEG]---[7SEG]

Do you need a schematic?
 
B

Bob Masta

Jan 1, 1970
0
I just had a wacko thought. Go to your nearest drugstore, Radio
Shack, or whatever, and pick up a cheap stopwatch built into a fairly
large case.

Build yourself a little "button pusher" -- maybe a reed relay circuit
-- driven when you want to start and stop the timing. Perform a
little microsurgery on the stopwatch to solder your button pusher
across the stopwatch's start/stop button.

Voila!

Or maybe one of those cheapo clocks (wristwatch or little giveaway
types) and see what happens if you disconnect and reconnect the
battery... if it starts countng seconds from 12:00:00 you are all set!


Back in the Olden Days when 4-function calculators first started
to become cheap, there were magazine articles on using them
for counters by faking a keypress. You might be able to use the
output of a 555 to provide the pulse, and just use the calculator
as the counter.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!
 
J

John Fields

Jan 1, 1970
0
I need to build a simple timer which simply counts elapsed time in
seconds as soon as current is turned on, then turns off and resets
when the power is disconnected. Or perhaps resets then begins counting
elapsed seconds, then shuts off when the power is disconnected. I
would like to display the seconds on an LCD or LED screen about the
size of a spoon.
I have no experience with electronics but I am keen to learn!
Hopefully this will be the start of many gadgets...
I really appreciate your help. Thanks!!!

    What sort of accuracy do you need and how long will the timed period be?
(In other words, do you need "watch" accuracy, or within a couple of
percent, and how many digits will be needed to display the timed period?)
    The timing is relatively easy, depending on accuracy and the length of
the timed period, but the display will take a bit more work.
    For an LCD display, you would need a micro-controller, along with
programming skills, a compiler and a programmer and, of course, the other
hardware such as resistors, capacitors, diodes etc. Programmers and
compilers can cost a fair bit. Then you'd need to spend a bit of time
working up to the level you require. This method would provide the best
results, both in timing and quality of display, but is by far the most
expensive, especially if this is a small project.
    LED displays are simpler, but need a few more chips for counting,
decoding and LED display segment driving, dependent on the number of digits.
One thing to consider is whether the unit will be used in relative darkness
or daylight. LEDs are best for darker settings and LCDs are more suited to
lighter environments.
    A bit more info would help.
    ... Steve
Thanks for the reply Steve,
A bit more info...
The accuracy is not an issue for me so long as it is 'fairly'
accurate. The only thing I can liken it to is when you step out a
distance- "right, that's 20 metres give or take a couple.". A maximum
time to count to would be 99 seconds. I have read a little about the
555 timer so I think that's my guy, but as for how I can use it for
this application, I'm stumped.
I also like the suggestion for a couple of segment LCD's to display
it. I hope this is enough info to get me started. Thanks again!

---
This will work: (View in Courier)

   [7555]---[4510]---[4510]
              |        |
   [7555]-+-[4543]---[4543]        
          |   |        |
          +-[7SEG]---[7SEG]

Do you need a schematic?

Hi John,

Yes- a schematic would be great! Just looking into it now can you
correct my logic?
7555 (provides timed pulses)-----4510(converts pulses to binary
code)-----4543(converts binary code to drive 7 seg)-----7 seg(displays
4543 input).
A couple of questions:
-How can you set the 7555 to count seconds?

---
I've posted a schematic for you on
alt.binaries.schematics.electronic, and R5 is used to set the timer
clock frequency.
---
-How can this be reset before each count?

---
I don't understand. Do you want to have, say, a pushbutton which,
when it's pressed and released will cause the count to go to zero
and then start counting up again?

If so, then probably the easiest way would be to rewire the 4510s'
RESETs like this: (View in Courier)


Vcc
| U2
| <--+ +----+
| | | |
O [C3] | |
| | | |
+----+---|R |
| +----+
|
| U5
| +----+
| | |
| | |
| | |
+---|R |
| +----+
|
[R3]
|
GND

then get rid of R1, C1, and C4, and connect the 7555's RESETS to
Vcc.
---
-How on earth can I build it????

---
Probably the easiest way for you, since you're just starting out,
would be to use one of those plastic breadboard thingies you can
plug components and wires into to connect things up.

If you go to:

http://www.elenco.com/

and then click on "Electronics Division", then on "Breadboard and
Prototyping" and finally on any of the first ten entries in the
"Item" column you'll see what I mean.

For an example of how they're used, goto:

http://www.kpsec.freeuk.com/breadb.htm
---
 
Hi,
I need to build a simple timer which simply counts elapsed time in
seconds as soon as current is turned on, then turns off and resets
when the power is disconnected. Or perhaps resets then begins counting
elapsed seconds, then shuts off when the power is disconnected. I
would like to display the seconds on an LCD or LED screen about the
size of a spoon.
I have no experience with electronics but I am keen to learn!
Hopefully this will be the start of many gadgets...
I really appreciate your help. Thanks!!!
-Ben
    What sort of accuracy do you need and how long will the timed period be?
(In other words, do you need "watch" accuracy, or within a couple of
percent, and how many digits will be needed to display the timed period?)
    The timing is relatively easy, depending on accuracy and thelength of
the timed period, but the display will take a bit more work.
    For an LCD display, you would need a micro-controller, alongwith
programming skills, a compiler and a programmer and, of course, the other
hardware such as resistors, capacitors, diodes etc. Programmers and
compilers can cost a fair bit. Then you'd need to spend a bit of time
working up to the level you require. This method would provide the best
results, both in timing and quality of display, but is by far the most
expensive, especially if this is a small project.
    LED displays are simpler, but need a few more chips for counting,
decoding and LED display segment driving, dependent on the number ofdigits.
One thing to consider is whether the unit will be used in relative darkness
or daylight. LEDs are best for darker settings and LCDs are more suited to
lighter environments.
    A bit more info would help.
    ... Steve
Thanks for the reply Steve,
A bit more info...
The accuracy is not an issue for me so long as it is 'fairly'
accurate. The only thing I can liken it to is when you step out a
distance- "right, that's 20 metres give or take a couple.". A maximum
time to count to would be 99 seconds. I have read a little about the
555 timer so I think that's my guy, but as for how I can use it for
this application, I'm stumped.
I also like the suggestion for a couple of segment LCD's to display
it. I hope this is enough info to get me started. Thanks again!
---
This will work: (View in Courier)
   [7555]---[4510]---[4510]
              |        |
   [7555]-+-[4543]---[4543]        
          |   |        |
          +-[7SEG]---[7SEG]
Do you need a schematic?
Yes- a schematic would be great! Just looking into it now can you
correct my logic?
7555 (provides timed pulses)-----4510(converts pulses to binary
code)-----4543(converts binary code to drive 7 seg)-----7 seg(displays
4543 input).
A couple of questions:
-How can you set the 7555 to count seconds?

---
I've posted a schematic for you on
alt.binaries.schematics.electronic, and R5 is used to set the timer
clock frequency.
---
-How can this be reset before each count?

---
I don't understand.  Do you want to have, say, a pushbutton which,
when it's pressed and released will cause the count to go to zero
and then start counting up again?

If so, then probably the easiest way would be to rewire the 4510s'
RESETs like this: (View in Courier)

        Vcc
         |     U2
    | <--+   +----+    
    |    |   |    |
    O   [C3] |    |
    |    |   |    |
    +----+---|R   |
         |   +----+
         |
         |     U5
         |   +----+
         |   |    |
         |   |    |
         |   |    |
         +---|R   |
         |   +----+
         |
        [R3]
         |
        GND

then get rid of R1, C1, and C4, and connect the 7555's RESETS to
Vcc.
---
-How on earth can I build it????

---
Probably the easiest way for you, since you're just starting out,
would be to use one of those plastic breadboard thingies you can
plug components and wires into to connect things up.

If you go to:

http://www.elenco.com/

and then click on "Electronics Division", then on "Breadboard and
Prototyping" and finally on any of the first ten entries in the
"Item" column you'll see what I mean.

For an example of how they're used, goto:

http://www.kpsec.freeuk.com/breadb.htm
---
Very keen to learn about this frontier! Thanks for the assistance

Hi John,

Thank you very much for your help. However I am unable to get your
schematic (I have been at it for 2 hours!). Is there another place
where I can access it? Perhaps email? Thanks again -Ben
 
Top