# Random timer!

B

#### Baron

Jan 1, 1970
0
Hi Guys,

I'm looking for ideas here. I am trying to figure out how to make a
random interval timer! Something that will trigger an indicator
after a random period of time. Ideally 1 to 15 seconds after a button
is pushed.

Thanks.

J

#### Jan Nielsen

Jan 1, 1970
0
Baron said:
I'm looking for ideas here. I am trying to figure out how to make a
random interval timer! Something that will trigger an indicator
after a random period of time. Ideally 1 to 15 seconds after a button
is pushed.
A PICAXE 08 will do it, although if you dont seed the random with
something dynamic, it will be the same pattern after every boot.

The pic is 1.5gbp or so, programmed in basic or flowchart trough 2
resistors, so cheap to get started with.

http://www.rev-ed.co.uk/picaxe/

/Jan

J

#### Jasen

Jan 1, 1970
0
I'm looking for ideas here. I am trying to figure out how to make a
random interval timer! Something that will trigger an indicator
after a random period of time. Ideally 1 to 15 seconds after a button
is pushed.

have a fast oscilator the becomes a slow oscilator when the button is pressed.
(period of 14 seconds) add a 1 second delay

Bye.
Jasen

B

#### Baron

Jan 1, 1970
0
Hi Jasen, inscribed thus:
have a fast oscilator the becomes a slow oscilator when the button
is pressed. (period of 14 seconds) add a 1 second delay

Bye.
Jasen

I like that idea... but how would you implement it ?

B

#### Baron

Jan 1, 1970
0
Hi jan,

Jan Nielsen inscribed thus:
A PICAXE 08 will do it, although if you dont seed the random with
something dynamic, it will be the same pattern after every boot.

The pic is 1.5gbp or so, programmed in basic or flowchart trough 2
resistors, so cheap to get started with.

http://www.rev-ed.co.uk/picaxe/

/Jan

I've never used pickaxe. Thanks for the link, I'l go and have a look
at it.

J

#### John Fields

Jan 1, 1970
0
Hi Guys,

I'm looking for ideas here. I am trying to figure out how to make a
random interval timer! Something that will trigger an indicator
after a random period of time. Ideally 1 to 15 seconds after a button
is pushed.

---
Do you want it to be an integral number of seconds from when the
button is pushed or are you looking for a pulse with a truly random
width starting 1 second after the button is pushed and ending at any
time up to and including 15 seconds after the button was pushed?

B

#### Baron

Jan 1, 1970
0
Hello John,

John Fields inscribed thus:
---
Do you want it to be an integral number of seconds from when the
button is pushed or are you looking for a pulse with a truly random
width starting 1 second after the button is pushed and ending at any
time up to and including 15 seconds after the button was pushed?

This is intended as a reaction timing device. The user pushes a
button and after a random delay, pops a light on and starts a
counter. The user presses a second button that stops and freezes the
counter. A little like the "Simon" toy but with a counter instead of
a buzzer. Fixed delays ie 1, 2, 4 etc seconds is easy. I didn't
think a random delay would be so hard !

R

#### Rich Grise

Jan 1, 1970
0
John Fields inscribed thus:
This is intended as a reaction timing device. The user pushes a
button and after a random delay, pops a light on and starts a
counter. The user presses a second button that stops and freezes the
counter. A little like the "Simon" toy but with a counter instead of
a buzzer. Fixed delays ie 1, 2, 4 etc seconds is easy. I didn't
think a random delay would be so hard !

Just use a PSRG (pseudorandom number generator). Let it free-run, and
when the button is pressed, use the PSRG's current value to select one

Good Luck!
Rich

J

#### John Fields

Jan 1, 1970
0
Hello John,

John Fields inscribed thus:

This is intended as a reaction timing device. The user pushes a
button and after a random delay, pops a light on and starts a
counter. The user presses a second button that stops and freezes the
counter. A little like the "Simon" toy but with a counter instead of
a buzzer. Fixed delays ie 1, 2, 4 etc seconds is easy. I didn't
think a random delay would be so hard !

---
It isn't, it's just that your description is confusing and isn't
detailed enough to allow a design to be done.

From your second description I take it that you want a device which,
after a button (START) is pushed, waits for between 1 second and 15
seconds to turn on a light and simultaneously start a counter then,
when a second button (STOP) is pressed, stops the counter while
preserving the value of the count it has accumulated.

What you haven't said is whether you want the delay to occur in
random increments of one second and what granularity you want from
the reaction time counter. That is, 1s? 100ms? 10ms? ???

You also haven't addressed how you want the reaction time counter to
be reset if you're doing multiple runs.

A good way to do it would be to have the START button do it at the
beginning of each run, unless you have a better idea.

J

#### John Fields

Jan 1, 1970
0
On Fri, 01 Jun 2007 22:37:08 +0100, Baron

---
It isn't, it's just that your description is confusing and isn't
detailed enough to allow a design to be done.

From your second description I take it that you want a device which,
after a button (START) is pushed, waits for between 1 second and 15
seconds to turn on a light and simultaneously start a counter then,
when a second button (STOP) is pressed, stops the counter while
preserving the value of the count it has accumulated.

What you haven't said is whether you want the delay to occur in
random increments of one second and what granularity you want from
the reaction time counter. That is, 1s? 100ms? 10ms? ???

You also haven't addressed how you want the reaction time counter to
be reset if you're doing multiple runs.

A good way to do it would be to have the START button do it at the
beginning of each run, unless you have a better idea.
---
I've made a few assumptions and posted a schematic to abse.

The device should work like this:

1. When the START button is pushed, a four-bit pseudo-randomly
generated number is loaded into a four bit binary delay counter
and the counter enabled.

2. The PRSG is advanced to the next state.

3. The counter's one second clock is started.

4. The four BCD digit reaction time counter's outputs are cleared.

When the delay counter times out:

1. The delay timer is disabled and latched up.

2. An LED is turned on.

3. The reaction time counter is enabled.

4. The 1000Hz reaction counter clock is started.

When the STOP button is pressed:

1. The reaction time counter is disabled and its outputs frozen in
the state they were in when the STOP button was pressed.

When the START button is pressed again, the new pseudo-random number
will be loaded into the delay counter and the cycle started anew.

One caveat: One of the allowed states of the PSRG is 1111, which
will cause the LED to come on as soon as the START button is
pressed, so instead of 15 random delays from 1 second to 15 seconds
you'll have 16 random delays from zero seconds to 15 seconds.

It's a feature, not a bug.

B

#### Baron

Jan 1, 1970
0
John Fields inscribed thus:
---
I've made a few assumptions and posted a schematic to abse.

The device should work like this:

1. When the START button is pushed, a four-bit pseudo-randomly
generated number is loaded into a four bit binary delay counter
and the counter enabled.

2. The PRSG is advanced to the next state.

3. The counter's one second clock is started.

4. The four BCD digit reaction time counter's outputs are cleared.

When the delay counter times out:

1. The delay timer is disabled and latched up.

2. An LED is turned on.

3. The reaction time counter is enabled.

4. The 1000Hz reaction counter clock is started.

When the STOP button is pressed:

1. The reaction time counter is disabled and its outputs frozen in
the state they were in when the STOP button was pressed.

When the START button is pressed again, the new pseudo-random number
will be loaded into the delay counter and the cycle started anew.

One caveat: One of the allowed states of the PSRG is 1111, which
will cause the LED to come on as soon as the START button is
pressed, so instead of 15 random delays from 1 second to 15 seconds
you'll have 16 random delays from zero seconds to 15 seconds.

It's a feature, not a bug.

Hi John,

Unfortunately abse (alt.binaries.schematics.electronics) is not a
services any more. First they stopped posting and now they have been
discontinued altogether. This server is the only one I can read and
post to.

B

#### Baron

Jan 1, 1970
0
John Fields inscribed thus:

Yes that's it exactly

The clock to the counter is at 1Khz.

That is what I am doing now. Pushing the start button resets the
counter to zero.
---
I've made a few assumptions and posted a schematic to abse.

The device should work like this:

1. When the START button is pushed, a four-bit pseudo-randomly
generated number is loaded into a four bit binary delay counter
and the counter enabled.

This is the bit that I am struggling with !
2. The PRSG is advanced to the next state.

3. The counter's one second clock is started.

4. The four BCD digit reaction time counter's outputs are cleared.

When the delay counter times out:

1. The delay timer is disabled and latched up.

2. An LED is turned on.

3. The reaction time counter is enabled.

4. The 1000Hz reaction counter clock is started.

When the STOP button is pressed:

1. The reaction time counter is disabled and its outputs frozen in
the state they were in when the STOP button was pressed.

When the START button is pressed again, the new pseudo-random number
will be loaded into the delay counter and the cycle started anew.

One caveat: One of the allowed states of the PSRG is 1111, which
will cause the LED to come on as soon as the START button is
pressed, so instead of 15 random delays from 1 second to 15 seconds
you'll have 16 random delays from zero seconds to 15 seconds.

It's a feature, not a bug.

Sounds good !

M

#### Michael A. Terrell

Jan 1, 1970
0
Baron said:
Unfortunately abse (alt.binaries.schematics.electronics) is not a
services any more. First they stopped posting and now they have been
discontinued altogether. This server is the only one I can read and
post to.

http://www.usenet-replayer.com/groups/index.html

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

J

#### John Fields

Jan 1, 1970
0
Hi John,

Unfortunately abse (alt.binaries.schematics.electronics) is not a
services any more. First they stopped posting and now they have been
discontinued altogether. This server is the only one I can read and
post to.

B

#### Baron

Jan 1, 1970
0
John Fields inscribed thus:
Done ! Thank you John.

J

#### Jasen

Jan 1, 1970
0
Hi Jasen, inscribed thus:

I like that idea... but how would you implement it ?

I'd probably do it software, but if pressed to do it in hardware
it'd be based around this:

here's the variable-rate bit done using a LM555 tiomer chip,

(it's not perfect one time in 1000 (or so) it'll fire immediately instead of
waiting "randomly" 0-14 seconds but I'm guessing from your description
that's not an issue...

.-------------------------------------------------------------.
| This is an ascii schematic, if the diagram appears garbled |
| try switching to a fixed-pitch font (courier works well) |
| pasting it into notepad works well on ms-windows. |
| or in google groups "view source" (found under options) |
-------------------------------------------------------------'

500K slow rate
\
/\
.-\/\/\--+--------+--- +5V
| / | |
/ | . . . .|. . . .
\ | . VCC(8) .
/ 1.2M | . .
\ --RES(4) OUT(3)--------->
| . 555 .
go-fast ----\/\/\-->|-+--------+--TH(6) DIS(7)-----.
10K 1N914 | . . |
+--TR(2) CV(5)-- |
| . . |
| . GND(1) . |
| . . . .|. . . . |
| | |
+--------|-----\/\/\-'
| | 33
===== |
10uF | |
--+--------+-- 0V

+5V on go fast will make it run at about 100Hz - faster than human
reactions.

pur 0V on go fast and the rate is determined by the trimmer at the
top, set that so that the circuit pulses once every 14 seconds with
go-fast held low. (best way to detect the pulses may be cheap
headphones in series with a 1K resistor on the output, the pulse will
it'll probably be too short to easily see on a LED)

the rest of the circuit depends on exactly what you want.

assuming the start switch is a momentary push button,
is it acceptable to require that the operator to hold it down
until the random trigger ?

can I use a two pole switch to make the design easier or is only
single pole available, can the switch be floating or must one end be
ground or +5v

what sort of output do you need is a floating LED acceptable or must
it be ground referenced ?

what behavior do you want from the output?

Bye.
Jasen

B

#### Baron

Jan 1, 1970
0
Jasen inscribed thus:
I'd probably do it software, but if pressed to do it in hardware
it'd be based around this:

here's the variable-rate bit done using a LM555 tiomer chip,

(it's not perfect one time in 1000 (or so) it'll fire immediately
instead of waiting "randomly"Â 0-14 seconds but I'm guessing from
your description that's not an issue...

.-------------------------------------------------------------.
| This is an ascii schematic, if the diagram appears garbled |
| try switching to a fixed-pitch font (courier works well) |
| pasting it into notepad works well on ms-windows. |
| or in google groups "view source" (found under options) |
-------------------------------------------------------------'

Yes I have been caught out by not using fixed pitch fonts before !
500K slow rate
\
/\
.-\/\/\--+--------+--- +5V
| / | |
/ | . . . .|. . . .
\ | . VCC(8) .
/ 1.2M | . .
\ --RES(4) OUT(3)--------->
| . 555 .
go-fast ----\/\/\-->|-+--------+--TH(6) DIS(7)-----.
10K 1N914 | . . |
+--TR(2) CV(5)-- |
| . . |
| . GND(1) . |
| . . . .|. . . . |
| | |
+--------|-----\/\/\-'
| | 33
===== |
10uF | |
--+--------+-- 0V

+5V on go fast will make it run at about 100Hz - faster than human
reactions.

pur 0V on go fast and the rate is determined by the trimmer at the
top, set that so that the circuit pulses once every 14 seconds
with go-fast held low. (best way to detect the pulses may be cheap
headphones in series with a 1K resistor on the output, the pulse
will it'll probably be too short to easily see on a LED)

the rest of the circuit depends on exactly what you want.

The indicator and counter should come on together !
assuming the start switch is a momentary push button,
is it acceptable to require that the operator to hold it down
until the random trigger ?

No ! Once pushed the operator has to be able to press a second
button. This stops the counter and latches the display until the
first button is pressed again.
can I use a two pole switch to make the design easier or is only
single pole available, can the switch be floating or must one end
be ground or +5v

The switches I used are the momentary ones from computer reset
buttons.
what sort of output do you need is a floating LED acceptable or
must it be ground referenced ?

What happens at the moment is a monostable flips state, 0 - 5v TTL
logic.
what behavior do you want from the output?

Bye.
Jasen

It won't take me long to breadboard this up so that I can play with
it. If it works well then that will be great.

B

#### Bob Masta

Jan 1, 1970
0
John Fields inscribed thus:

This is the bit that I am struggling with !

Jasen's original suggestion makes a great pseudo-random generator.
Just have a 4-bit counter counting a fast clock. When the START
button is hit, the counter will be at some random value (random
due to the random timing of the START press relative to the
high-speed clock). You just have to switch off that clock and
switch to a low-speed clock for your count-down. (You can
switch the timing values in a single clock, or have 2 separate
clocks for this.)

Best regards,

Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator

B

#### Baron

Jan 1, 1970
0
Hi Bob,

Bob Masta inscribed thus:
Jasen's original suggestion makes a great pseudo-random generator.
Just have a 4-bit counter counting a fast clock. When the START
button is hit, the counter will be at some random value (random
due to the random timing of the START press relative to the
high-speed clock). You just have to switch off that clock and
switch to a low-speed clock for your count-down. (You can
switch the timing values in a single clock, or have 2 separate
clocks for this.)

Best regards,

Bob Masta

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator

This seems silly ! But I just can't seem get my head around it ! This
is what I have at the moment.

I have a 1Khz clock and a one second gate time which feeds a four
digit display. The one second clock is counted by a four bit counter
to give 1, 2, 4, 8, seconds delay using diodes and a switch to select
1 to 16 seconds.

The display is four digits fed from the 1Khz clock gated by the 1
second clock. This is started by a monostable triggered from the
delay timer and triggered back by the stop button.

This works fine. I just don't seem to be able to see the wood for the
trees !

J

#### John Fields

Jan 1, 1970
0
I have a 1Khz clock and a one second gate time which feeds a four
digit display. The one second clock is counted by a four bit counter
to give 1, 2, 4, 8, seconds delay using diodes and a switch to select
1 to 16 seconds.

The display is four digits fed from the 1Khz clock gated by the 1
second clock. This is started by a monostable triggered from the
delay timer and triggered back by the stop button.

This works fine. I just don't seem to be able to see the wood for the
trees !

---
For some reason I didn't get your email addy, so if you'll send it
again (or post it here with sufficient munging to foil the
harvesters) I'll be able to send you my circuit.

BTW, here's the PRSG in LTSPICE, with a fix so it has a minimum
delay of 1 second (the "feature" was fixed :

Version 4
SHEET 1 2076 1144
WIRE 480 -816 -352 -816
WIRE 592 -816 480 -816
WIRE 752 -816 672 -816
WIRE -416 -768 -592 -768
WIRE 240 -752 -352 -752
WIRE 240 -704 240 -752
WIRE 592 -704 240 -704
WIRE 752 -704 752 -816
WIRE 752 -704 672 -704
WIRE 240 -640 240 -704
WIRE 240 -640 -352 -640
WIRE 0 -608 -352 -608
WIRE -416 -592 -528 -592
WIRE 0 -592 0 -608
WIRE 592 -592 0 -592
WIRE 752 -592 752 -704
WIRE 752 -592 672 -592
WIRE -256 -576 -352 -576
WIRE -592 -528 -592 -768
WIRE -528 -528 -528 -592
WIRE -256 -496 -256 -576
WIRE 592 -496 -256 -496
WIRE 752 -496 752 -592
WIRE 752 -496 672 -496
WIRE -128 -480 -384 -480
WIRE 128 -480 -128 -480
WIRE 368 -480 128 -480
WIRE 512 -480 368 -480
WIRE -384 -432 -384 -480
WIRE -128 -432 -128 -480
WIRE 128 -432 128 -480
WIRE 368 -432 368 -480
WIRE -544 -384 -544 -464
WIRE -464 -384 -544 -384
WIRE -256 -384 -256 -496
WIRE -256 -384 -304 -384
WIRE -208 -384 -256 -384
WIRE 0 -384 0 -592
WIRE 0 -384 -48 -384
WIRE 48 -384 0 -384
WIRE 240 -384 240 -640
WIRE 240 -384 208 -384
WIRE 288 -384 240 -384
WIRE 480 -384 480 -816
WIRE 480 -384 448 -384
WIRE 752 -384 752 -496
WIRE -496 -336 -624 -336
WIRE -464 -336 -496 -336
WIRE -208 -336 -240 -336
WIRE 48 -336 16 -336
WIRE 288 -336 256 -336
WIRE -624 -320 -624 -336
WIRE -496 -256 -496 -336
WIRE -240 -256 -240 -336
WIRE -240 -256 -496 -256
WIRE 16 -256 16 -336
WIRE 16 -256 -240 -256
WIRE 256 -256 256 -336
WIRE 256 -256 16 -256
WIRE -624 -208 -624 -240
WIRE -384 -208 -384 -288
WIRE -384 -208 -624 -208
WIRE -128 -208 -128 -288
WIRE -128 -208 -384 -208
WIRE 128 -208 128 -288
WIRE 128 -208 -128 -208
WIRE 368 -208 368 -288
WIRE 368 -208 128 -208
WIRE 512 -208 512 -480
WIRE 512 -208 368 -208
WIRE 752 -208 752 -304
WIRE 752 -208 512 -208
WIRE -624 -176 -624 -208
FLAG -624 -176 0
SYMBOL Digital\\dflop -384 -432 R0
SYMATTR InstName A1
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL voltage -624 -336 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(0 5 0 50e-9 50e-9 .5 1)
SYMATTR InstName V1
SYMBOL Digital\\dflop -128 -432 R0
SYMATTR InstName A2
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\dflop 128 -432 R0
SYMATTR InstName A3
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\dflop 368 -432 R0
SYMATTR InstName A4
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\xor -400 -720 R180
SYMATTR InstName A5
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\and -384 -672 M0
SYMATTR InstName A6
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL Digital\\xor -496 -480 R90
SYMATTR InstName A7
SYMATTR SpiceLine vhigh 5v trise 88e-9 tfall 88e-9
SYMBOL res 688 -832 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R1
SYMATTR Value 160k
SYMBOL res 688 -720 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R2
SYMATTR Value 80k
SYMBOL res 688 -608 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R3
SYMATTR Value 40k
SYMBOL res 688 -512 R90
WINDOW 0 -34 58 VBottom 0
WINDOW 3 -35 57 VTop 0
SYMATTR InstName R4
SYMATTR Value 20k
SYMBOL res 736 -400 R0
SYMATTR InstName R5
SYMATTR Value 330
TEXT -584 -184 Left 0 !.tran 20

When you run it, The horizontal axis corresponds to successive
pressings of the START switch (after the STOP switch has been
pressed) and the vertical axis corresponds to the numerical value of
the shift register's output, where 10mV = 1, 20mV = 2, and so on.

The resistor network is a DAC used to generate the vertical data and
isn't used in the actual circuit.

T
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