Turning a light on and off with momentary switch

[Chris W]

I want a circuit that will turn a light on with the press of a momentary
switch and then turn it back off when the momentary switch is hit
again. I had heard that a flip flop might be the way to go. After some
reading, I have found that a flip flop is a much more complex device
than I was lead to believe. I think a flip flop would some how do the
job, but it is going to take some more reading before I figure out how.
If you have been reading some of my other posts, you know that I want to
turn on and off more than one light, so I need several of these
circuits, preferably using the minimum number of components.

Another option I would like to explore is to turn the light on and off
using 2 inputs. Say we have in put A and B. If input B is high, when
input A goes high, turn the light on, or leave it on. If input B is
low, when input A goes hight, turn the light off, or leave it off.

--
Chris W

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
http://thewishzone.com

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

 

Chris W wrote:

I want a circuit that will turn a light on with the press of a
momentary
switch and then turn it back off when the momentary switch is hit
again. I had heard that a flip flop might be the way to go. After
some
reading, I have found that a flip flop is a much more complex device
than I was lead to believe. I think a flip flop would some how do
the
job, but it is going to take some more reading before I figure out
how.
If you have been reading some of my other posts, you know that I want
to
turn on and off more than one light, so I need several of these
circuits, preferably using the minimum number of components.

Another option I would like to explore is to turn the light on and
off
using 2 inputs. Say we have in put A and B. If input B is high,
when
input A goes high, turn the light on, or leave it on. If input B is
low, when input A goes hight, turn the light off, or leave it off.

--
Chris W

Yes, a flip-flop would do it and someone is sure to suggest a PIC, both
requiring a fair amount of extra components to actually work. Have you
looked for alternate action switches or relays? It would run your
lights and not require a degree to get it to work.
Glenn Gundlach

 

[Si Ballenger]

On Wed, 16 Feb 2005 18:12:59 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:

Yes, a flip-flop would do it and someone is sure to suggest a PIC, both
requiring a fair amount of extra components to actually work. Have you
looked for alternate action switches or relays? It would run your
lights and not require a degree to get it to work.
Glenn Gundlach


Is that because flip-flops require capacitors to store state information? I
would be interested to know the minimum complement of components necessary
to support a single flip-flop. Perhaps there is a good link to this kind of
information (?)

I have a similar request as the original poster. I would like to use a
momentary switch to cycle among three LEDs. Is the circuit design for this
using flip-flops complex? Is there an easier way to generate the same
functionality? It seems that there must be some ICs out there that provide
this kind of functionality out of the box. Does anyone know of any?

Thanks a lot!
Peter

You can use an led chaser kit to do the sequental leds. You can
use just the first two outputs on the chip for flip-flop. I've
got a page below showing some tinkering with the 4017 decade
counter chip that might be useful.

http://www.geocities.com/zoomkat/RSswitcher.htm

 

[John Fields]

On Wed, 16 Feb 2005 18:12:59 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:

Yes, a flip-flop would do it and someone is sure to suggest a PIC, both
requiring a fair amount of extra components to actually work. Have you
looked for alternate action switches or relays? It would run your
lights and not require a degree to get it to work.
Glenn Gundlach


Is that because flip-flops require capacitors to store state information?

---
No.
---

I would be interested to know the minimum complement of components necessary
to support a single flip-flop.

---
Just one, the driver.
---

information (?)

I have a similar request as the original poster. I would like to use a
momentary switch to cycle among three LEDs. Is the circuit design for this
using flip-flops complex?

---
If you have to ask... Simple for me might be impossible for you, but
you haven't yet described what it is you expect the momentary switch
to do.
---

Is there an easier way to generate the same functionality?

---
What _functionality_?
---

It seems that there must be some ICs out there that provide
this kind of functionality out of the box. Does anyone know of any?

---
Pretty much any ľC...

--
John Fields

 

[Peter Michelson]

Thank you for your reply.

"John Fields" <jfields@austininstruments.com> wrote in message
news:q7n711p8kv1nthidjc2be6hcko1kn2kulh@4ax.com...

I would be interested to know the minimum complement of components
necessary
to support a single flip-flop.

---
Just one, the driver.
---
Is there a more specific term for "driver"? I am not familiar with a

component by that name.

I have a similar request as the original poster. I would like to use a
momentary switch to cycle among three LEDs. Is the circuit design for
this
using flip-flops complex?

---
If you have to ask... Simple for me might be impossible for you, but

Good point. Simple for me means that few (e.g., less than 5) components are
involved and testing can be done with a multimeter.

you haven't yet described what it is you expect the momentary switch
to do.
---

As I said, I would like to cycle among three LEDs. To elaborate: one LED is
turned on at any given time; each time I depress the momentary switch, I
would like the LED that is on to turn off, and the next LED in sequence to
turn on; the first LED is considered to follow the third in a cyclical
manner. I imagine that this circuit is functionally similar to one that
would drive marquis lights, except that instead of using a timer chip, it is
user-driven.

Is there an easier way to generate the same functionality?

---
What _functionality_?
---

I hope the more complete description above is easier to understand than the
one in my first posting.

It seems that there must be some ICs out there that provide
this kind of functionality out of the box. Does anyone know of any?

---
Pretty much any ľC...

Is there one in particular that is best-suited to the functionality
described above?

--
John Fields

Thanks again for your reply.

 

[petrus bitbyter]

"Chris W" <1qazse4@cox.net> schreef in bericht
news:2OOQd.63983$jn.59042@lakeread06...

I want a circuit that will turn a light on with the press of a momentary
switch and then turn it back off when the momentary switch is hit again. I
had heard that a flip flop might be the way to go. After some reading, I
have found that a flip flop is a much more complex device than I was lead
to believe. I think a flip flop would some how do the job, but it is going
to take some more reading before I figure out how. If you have been
reading some of my other posts, you know that I want to turn on and off
more than one light, so I need several of these circuits, preferably using
the minimum number of components.
Another option I would like to explore is to turn the light on and off
using 2 inputs. Say we have in put A and B. If input B is high, when
input A goes high, turn the light on, or leave it on. If input B is low,
when input A goes hight, turn the light off, or leave it off.

--
Chris W

Gift Giving Made Easy
Get the gifts you want & give the gifts they want
http://thewishzone.com

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." -- Benjamin Franklin, 1759
Historical Review of Pennsylvania

Chris,

What kind of lights do you want to switch? It makes a lot of difference
whether you want to switch a LED (~40mW) or a 100W incandescent bulb.

The most simple solution I can imagine is a tablelamp pushbutton switch.
Conrad sells them for ?2,20 but I guess you can do cheaper locally. It does
exactly what you describe. Push on, push off, push on, push off and so on.

A more expensive but still simple solution goes with a relay of the same
voltage as the lamp, a make- and a break pushbutton. Conrad sells relay from
below ?2,-- upward and pushbuttons from below ?1,00 upward depending on
voltages and currents required. Digikey will sell similar components but I
have no catalog at hand.

LEDs can be controlled easily using electronics and that's where the
flip-flop appears. You need a so called T-flipflop but they are not very
common. Use an D-type flipflop instead and connect the inverted Q-output
(/Q) to the D-input. Every pulse on the clock input will make the flipflop
change state. So a pushbutton on that input will theoretically do the job.
But a flipflop is a high speed switching device and will see a lot of pulses
every time you push and you can not predict the last one. So you need to
debounce your pushbutton carefully which requires some extra electronics.

Of course you can use a microcontoller as wel. Microchip sells 6 pins ones
these days and the only extra components you need is the pushbutton, the LED
and maybe two resistors. The problem of course is skills and equipment to
program them.

petrus bitbyter

 

[John Fields]

On Wed, 16 Feb 2005 19:33:08 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:

Thank you for your reply.

"John Fields" <jfields@austininstruments.com> wrote in message
news:q7n711p8kv1nthidjc2be6hcko1kn2kulh@4ax.com...

I would be interested to know the minimum complement of components
necessary
to support a single flip-flop.

---
Just one, the driver.
---
Is there a more specific term for "driver"? I am not familiar with a
component by that name.

---
The driver would be the device/circuit sending the information to the
flip-flop which would cause it to flip or flop.
---

I have a similar request as the original poster. I would like to use a
momentary switch to cycle among three LEDs. Is the circuit design for
this
using flip-flops complex?

---
If you have to ask... Simple for me might be impossible for you, but

Good point. Simple for me means that few (e.g., less than 5) components are
involved and testing can be done with a multimeter.

--
OK
--

you haven't yet described what it is you expect the momentary switch
to do.
---

As I said, I would like to cycle among three LEDs. To elaborate: one LED is
turned on at any given time; each time I depress the momentary switch, I
would like the LED that is on to turn off, and the next LED in sequence to
turn on; the first LED is considered to follow the third in a cyclical
manner. I imagine that this circuit is functionally similar to one that
would drive marquis lights, except that instead of using a timer chip, it is
user-driven.

---
"Marquee" lights?^)
---

Is there an easier way to generate the same functionality?

---
What _functionality_?
---

I hope the more complete description above is easier to understand than the
one in my first posting.

---
Yes, it is.

I'll reply, tomorrow or the day after, with a schematic which will
solve your problem.

Thanks again for your reply.

You're welcome.

--
John Fields

 

[John]

"Peter Michelson" <pete77r@hotmail.com> wrote in message
news:bDRQd.9917$Ps.1740@okepread06...

Thank you for your reply.

"John Fields" <jfields@austininstruments.com> wrote in message
news:q7n711p8kv1nthidjc2be6hcko1kn2kulh@4ax.com...

I would be interested to know the minimum complement of components
necessary
to support a single flip-flop.

---
Just one, the driver.
---
Is there a more specific term for "driver"? I am not familiar with a
component by that name.

A flip-flop basically stores a 1 or a 0, ON or OFF, respectively. It can't
switch between the two by itself. It needs additional circuitry to drive it,
or basically tell it when to switch the flip-flop from 0 to 1, and 1 to 0.

I have a similar request as the original poster. I would like to use a
momentary switch to cycle among three LEDs. Is the circuit design for
this
using flip-flops complex?

---
If you have to ask... Simple for me might be impossible for you, but

Good point. Simple for me means that few (e.g., less than 5) components
are
involved and testing can be done with a multimeter.

A component might be an IC, or a PIC which might be pretty advanced for an
electronics hobbyst.

you haven't yet described what it is you expect the momentary switch
to do.
---

As I said, I would like to cycle among three LEDs. To elaborate: one LED
is
turned on at any given time; each time I depress the momentary switch, I
would like the LED that is on to turn off, and the next LED in sequence to
turn on; the first LED is considered to follow the third in a cyclical
manner. I imagine that this circuit is functionally similar to one that
would drive marquis lights, except that instead of using a timer chip, it
is
user-driven.

A PIC would suit perfectly for this type of application but it requires some
funds for a PIC programmer (hardware) and coding the PIC (software). You'd
have to know how to program to use a PIC.

Is there an easier way to generate the same functionality?

---
What _functionality_?
---

I hope the more complete description above is easier to understand than
the
one in my first posting.


It seems that there must be some ICs out there that provide
this kind of functionality out of the box. Does anyone know of any?

---
Pretty much any ľC...

Is there one in particular that is best-suited to the functionality
described above?

--
John Fields

Thanks again for your reply.

 

[Peter Michelson]

Thank you for your reply.

"John" <welcomehowcome@hotmail.com> wrote in message
news:tZGdndwvwJ8XaY7fRVn-3A@comcast.com...

Is there a more specific term for "driver"? I am not familiar with a
component by that name.

A flip-flop basically stores a 1 or a 0, ON or OFF, respectively. It can't
switch between the two by itself. It needs additional circuitry to drive
it,
or basically tell it when to switch the flip-flop from 0 to 1, and 1 to 0.

what are the characteristics of the signal required to cause the bit to

change?

A PIC would suit perfectly for this type of application but it requires
some
funds for a PIC programmer (hardware) and coding the PIC (software). You'd
have to know how to program to use a PIC.

Does PIC stand for Programmable IC? Is this similar to an EPROM or PROM?
How much does PIC programmer hardware cost?

What skills are necessary for programming to use a PIC? For example, if one
is versed in machine language, is that sufficient?

Thanks for the information. It sounds intriguing.
Regards,
Peter

 

[Chris W]

petrus bitbyter wrote:

Chris,

What kind of lights do you want to switch? It makes a lot of
difference whether you want to switch a LED (~40mW) or a 100W
incandescent bulb.

For the first application I just want to switch 1 or maybe 2 LED's

hooked in parallel. They could be of different colors and therefore
different voltages so I am guessing even for just one led on each line I
probably need some kind of a driver so I can match the voltage and
current for each load. Future applications will need to switch around
10W lights, probably in the form of groups of LEDs, on and off.

LEDs can be controlled easily using electronics and that's where the
flip-flop appears. You need a so called T-flipflop but they are not
very common. Use an D-type flipflop instead and connect the inverted
Q-output (/Q) to the D-input. Every pulse on the clock input will make
the flipflop change state. So a pushbutton on that input will
theoretically do the job. But a flipflop is a high speed switching
device and will see a lot of pulses every time you push and you can
not predict the last one. So you need to debounce your pushbutton
carefully which requires some extra electronics.

After some more reading on flip flops I figured this out on my own. If
you read my post in 2-14-2005, you can read more about my application.
What I would really like to find is an IC with as many as 16 D flip
flops that are already wired up like you described. I don't suppose
finding that is likely?

Of course you can use a microcontoller as wel. Microchip sells 6 pins
ones these days and the only extra components you need is the
pushbutton, the LED and maybe two resistors. The problem of course is
skills and equipment to program them.

I'm thinking about getting one of the RABBIT modules, that way I don't
think I need a separate programmer do I?

--
Chris W

Gift Giving Made Easy
Get the gifts you want &
give the gifts they want
http://thewishzone.com

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

 

[John]

"Peter Michelson" <pete77r@hotmail.com> wrote in message
news:WxVQd.10007$Ps.3033@okepread06...

Thank you for your reply.

"John" <welcomehowcome@hotmail.com> wrote in message
news:tZGdndwvwJ8XaY7fRVn-3A@comcast.com...

Is there a more specific term for "driver"? I am not familiar with a
component by that name.

A flip-flop basically stores a 1 or a 0, ON or OFF, respectively. It
can't
switch between the two by itself. It needs additional circuitry to drive
it,
or basically tell it when to switch the flip-flop from 0 to 1, and 1 to
0.

what are the characteristics of the signal required to cause the bit to
change?

A flip-flop STORES a signal. So basically it stores whatever signal you feed
it. For your project, you don't need a flip-flop if you use a PIC.

A PIC would suit perfectly for this type of application but it requires
some
funds for a PIC programmer (hardware) and coding the PIC (software).
You'd
have to know how to program to use a PIC.

Does PIC stand for Programmable IC? Is this similar to an EPROM or PROM?
How much does PIC programmer hardware cost?

Yes. EPROM. You can get one for around $150US
(http://xtronics.com/memory/EPROM.htm)

What skills are necessary for programming to use a PIC? For example, if
one
is versed in machine language, is that sufficient?

Some are assembler, some are C/C+, some you can use BASIC.

Thanks for the information. It sounds intriguing.
Regards,
Peter

Microcontrollers are the easiest ways to create your own electronics devices
given you know how to program.

 

[petrus bitbyter]

"Chris W" <1qazse4@cox.net> schreef in bericht
news:vJWQd.64020$jn.59932@lakeread06...

petrus bitbyter wrote:


Chris,

What kind of lights do you want to switch? It makes a lot of difference
whether you want to switch a LED (~40mW) or a 100W incandescent bulb.

For the first application I just want to switch 1 or maybe 2 LED's hooked
in parallel. They could be of different colors and therefore different
voltages so I am guessing even for just one led on each line I probably
need some kind of a driver so I can match the voltage and current for each
load. Future applications will need to switch around 10W lights, probably
in the form of groups of LEDs, on and off.

One or two LEDs in series can be driven by some logic devices. For more LEDs
or lamps you will need a transistor driver or a relay.

LEDs can be controlled easily using electronics and that's where the
flip-flop appears. You need a so called T-flipflop but they are not very
common. Use an D-type flipflop instead and connect the inverted Q-output
(/Q) to the D-input. Every pulse on the clock input will make the
flipflop change state. So a pushbutton on that input will theoretically
do the job. But a flipflop is a high speed switching device and will see
a lot of pulses every time you push and you can not predict the last one.
So you need to debounce your pushbutton carefully which requires some
extra electronics.

After some more reading on flip flops I figured this out on my own. If
you read my post in 2-14-2005, you can read more about my application.
What I would really like to find is an IC with as many as 16 D flip flops
that are already wired up like you described. I don't suppose finding
that is likely?

Missed your post of 2-14-2005. Can't even find it in the Google groups.

AFAIK such a device does not exist and its very unlikely you'll ever find
one. You can design one for yourself using PLDs but that requires quite some
skills and programming equipment. Especially if you want to incorporate
debouncing. Even then you wil need power drivers to control loads over some
hundreds of mW.

Of course you can use a microcontoller as wel. Microchip sells 6 pins
ones these days and the only extra components you need is the pushbutton,
the LED and maybe two resistors. The problem of course is skills and
equipment to program them.

I'm thinking about getting one of the RABBIT modules, that way I don't
think I need a separate programmer do I?

FAIK RABBIT devices also requires programming which can be done using C. You
will also need a pretty expensive development system and the modules
themselves does look like to be cheap either.

Did you realise a module like you want, needs at least 34 pins? I think a 40
pins micro comes most close to that. A PIC16F877 is one of the cheaper
<$10,-- examples. Software is free from Microchip and programming tools can
be bought or home made. You can find a lot of information on
http://www.voti.nl/swp/n_index.html
but it's for sure not the only one a the on the net.

--
Chris W

Gift Giving Made Easy
Get the gifts you want & give the gifts they want
http://thewishzone.com

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." -- Benjamin Franklin, 1759
Historical Review of Pennsylvania

petrus bitbyter

 

[Peter Michelson]

"John Fields" <jfields@austininstruments.com> wrote in message
news:5vb911tha2ani58bp3au4686rm8mo5ocs0@4ax.com...

I'll reply, tomorrow or the day after, with a schematic which will
solve your problem.

That's very kind.


---

+-------------+
| 4017 |
| +-------+ |
VCC>--[100K]--O--> | +--|MR Q3|--+
| | |
O-----+--------|CP0 Q2|--[R3]--[LED3>]--+
| | | | |
| | | Q1|--[R2]--[LED2>]--+
[0.1] [1M] | | |
| | +-O|CP1 Q0|--[R1]--[LED1>]--+
| | | +-------+ |
GND>---------------+-----+-----+----------------------------+

Vcc - 2V
R1 = R2 = R3 = -----------
0.002A


All LEDs = HLMP4700


--
John Fields

That's great - thank you sincerely. It appears fairly simple and I look
forward to trying to implement it.

This is my first time reading a schematic in ascii, and it mostly makes
sense to me. My only question is what does "O" represent? For example,
there is an "O" next to CP1. Thanks for your patience.

Regards,
Peter

 

[John Fields]

On Thu, 17 Feb 2005 23:11:51 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:5vb911tha2ani58bp3au4686rm8mo5ocs0@4ax.com...
I'll reply, tomorrow or the day after, with a schematic which will
solve your problem.

That's very kind.


---

+-------------+
| 4017 |
| +-------+ |
VCC>--[100K]--O--> | +--|MR Q3|--+
| | |
O-----+--------|CP0 Q2|--[R3]--[LED3>]--+
| | | | |
| | | Q1|--[R2]--[LED2>]--+
[0.1] [1M] | | |
| | +-O|CP1 Q0|--[R1]--[LED1>]--+
| | | +-------+ |
GND>---------------+-----+-----+----------------------------+

Vcc - 2V
R1 = R2 = R3 = -----------
0.002A


All LEDs = HLMP4700


--
John Fields

That's great - thank you sincerely. It appears fairly simple and I look
forward to trying to implement it.

This is my first time reading a schematic in ascii, and it mostly makes
sense to me. My only question is what does "O" represent? For example,
there is an "O" next to CP1. Thanks for your patience.

---
The 'O' is used to represent what's called a 'low true' input. That
is, a desired result occurs as a result of that input being at a
logical '0'. In this case, that's zero volts or 'ground'

The other "O"s (at the switch) are just a convention used to denote a
switch (or relay) terminal.

--
John Fields

 

[John Fields]

On Thu, 17 Feb 2005 23:15:16 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:

"Bill Bowden" <wrongaddress@att.net> wrote in message
news:1108675337.245641.194540@o13g2000cwo.googlegroups.com...

There is a "10 stage LED sequencer" at the below address.
You will need to change the 555 oscillator into a
555 "one shot" circuit so you can use a pushbutton.

Thanks for the tip. I have used a 555 timer before, but I don't think I
ever used it as a one shot circuit, so I'd have to look that up.

The 4017 can be used for just 3 LEDs by connecting the
reset line (pin 15) to the 4th output, (pin 7).

Thanks - I think that's exactly the approach that John Fields took in his
schematic (see other posting in this thread).

---
Well, in all fairness, Bill's is better than mine in that he has a
single current limiting resistor as opposed to my three. Since only
one LED will be lit at any given time, there's only a need for one and
it can be connected from the common cathodes of the LEDs to ground.

He's suggested using a 555 to debounce the switch, but my simple RC
may work just as well. Depends on the switch's bounce
characteristics.

--
John Fields

 

[Rich Grise]

On Wed, 16 Feb 2005 15:19:19 -0600, Chris W wrote:

I want a circuit that will turn a light on with the press of a momentary
switch and then turn it back off when the momentary switch is hit
again. I had heard that a flip flop might be the way to go. After some
reading, I have found that a flip flop is a much more complex device
than I was lead to believe. I think a flip flop would some how do the
job, but it is going to take some more reading before I figure out how.
If you have been reading some of my other posts, you know that I want to
turn on and off more than one light, so I need several of these
circuits, preferably using the minimum number of components.

Another option I would like to explore is to turn the light on and off
using 2 inputs. Say we have in put A and B. If input B is high, when
input A goes high, turn the light on, or leave it on. If input B is
low, when input A goes hight, turn the light off, or leave it off.

What's your goal here? To learn about flip-flops, or to turn a light on
and off? If the latter, just get a push-on-push-off switch. PCs used to
have them - it's a mechanical action, a la a clicker ballpoint pen.

Cheers!
Rich

 

[Harold Ryan]

Hi Chris:

The circuit that you want to build consists of three sections. (1) The
momentary switch must be connected to a debounce circuit. This will create
only one edge when the switch is closed or opened. This is accomplished by
using a resistor and a cap to create a lowpass filter and a buffer logic
device like a 'AND' gate. The secret is to use an additional feed back
resistor that creates hysteresis.

The second section is the flip-flop that is wired to toggle. U can use a
74HC74 D type flip-flop or even a JK flip flop. The 3rd section is the
decode logic. If you want to just toggle an LED then there is no decode
logic. Just connect the output of the flip-flop to an LED or thru an
additional buffer chip. If you want to have 3 LEDS to sequence, just add
another flip-flop and use a couple NAND gates to decode the two outputs of
the two flip flops to generate 3 outputs. Use 74HCXXXX chips because the
crossover threshold voltage is 5volts/2 or 2.5 volts.

Harold



"Chris W" <1qazse4@cox.net> wrote in message
news:2OOQd.63983$jn.59042@lakeread06...

I want a circuit that will turn a light on with the press of a momentary
switch and then turn it back off when the momentary switch is hit again. I
had heard that a flip flop might be the way to go. After some reading, I
have found that a flip flop is a much more complex device than I was lead
to believe. I think a flip flop would some how do the job, but it is going
to take some more reading before I figure out how. If you have been
reading some of my other posts, you know that I want to turn on and off
more than one light, so I need several of these circuits, preferably using
the minimum number of components.
Another option I would like to explore is to turn the light on and off
using 2 inputs. Say we have in put A and B. If input B is high, when
input A goes high, turn the light on, or leave it on. If input B is low,
when input A goes hight, turn the light off, or leave it off.

--
Chris W

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Historical Review of Pennsylvania

 

[Peter Michelson]

Great explanation! Thank you for providing an architectural synopsis of
what's involved.
Peter

"Harold Ryan" <hryan@chartermi.net> wrote in message
news:9EyRd.1250$Mg6.1132@fe04.lga...

Hi Chris:

The circuit that you want to build consists of three sections. (1) The
momentary switch must be connected to a debounce circuit. This will create
only one edge when the switch is closed or opened. This is accomplished by
using a resistor and a cap to create a lowpass filter and a buffer logic
device like a 'AND' gate. The secret is to use an additional feed back
resistor that creates hysteresis.

The second section is the flip-flop that is wired to toggle. U can use a
74HC74 D type flip-flop or even a JK flip flop. The 3rd section is the
decode logic. If you want to just toggle an LED then there is no decode
logic. Just connect the output of the flip-flop to an LED or thru an
additional buffer chip. If you want to have 3 LEDS to sequence, just add
another flip-flop and use a couple NAND gates to decode the two outputs of
the two flip flops to generate 3 outputs. Use 74HCXXXX chips because the
crossover threshold voltage is 5volts/2 or 2.5 volts.

Harold

 

[Peter Michelson]

---
Well, in all fairness, Bill's is better than mine in that he has a
single current limiting resistor as opposed to my three. Since only
one LED will be lit at any given time, there's only a need for one and
it can be connected from the common cathodes of the LEDs to ground.

He's suggested using a 555 to debounce the switch, but my simple RC
may work just as well. Depends on the switch's bounce
characteristics.

--
John Fields

For me, there is educational value in seeing multiple approaches to the same
problem, particularly when someone explains the difference between the
various approaches, as you just did. So thank you.

Would you (or any other reader without commercial bias) please recommend an
inexpensive and reliable vendor for electronics parts for projects such as
this one? If such recommendations are not allowed on the newsgroup, please
feel free to email them to me.

Thank you,
Peter

 

[Robert Monsen]

Peter Michelson wrote:

Would you (or any other reader without commercial bias) please recommend an
inexpensive and reliable vendor for electronics parts for projects such as
this one? If such recommendations are not allowed on the newsgroup, please
feel free to email them to me.

Here are my links to electronics distributors (US bias)

http://www.acroname.com/
http://www.allcorp.com/
http://www.alliedelec.com/
http://www.aade.com/index.html
http://www.sciplus.com/?emailid=25
http://www.bgmicro.com/
http://store.yahoo.com/webtronics/index.html
http://www.componentkits.com/
http://www.elexp.com/
http://www.findchips.com/
http://www.futurlec.com/
http://www.jameco.com/
http://www.thelaserguy.com/index.html
http://www.mcminone.com/
http://www.meci.com/
http://www.mouser.com/
http://www.moyerelectronics.com/
http://www.mpja.com/
http://www.probemaster.com/
http://www.quickar.com/about.htm
http://www.quickar.com/index.php?session=
http://www.goldmine-elec.com/
http://www.commlinx.com.au/timing.htm
http://www.electronicsurplus.com/
http://alltronics.com/wire_and_cable.htm
http://home.att.net/~wzmicro/index.htm
http://www.alltronics.com/
http://www.lsdiodes.com/5mm/
http://www.hosfelt.com/

I usually use goldmine or futurlec for hobby parts. They don't mind
small orders, and don't charge me sales tax (I'm in california)

You can also get samples of parts from distributors like microchip,
analog, linear, national, fairchild, etc.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.