| Author |
Message |
Terry Pinnell
Guest
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 Posted:
Thu Feb 17, 2005 5:09 pm Post subject:
Re: Turning a light on and off with momentary switch |
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Chris W <1qazse4@cox.net> wrote:
| Quote: | 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.
|
Here are three practical circuits you can experiment with:
http://www.terrypin.dial.pipex.com/Images/Toggles-Momentary.gif
--
Terry Pinnell
Hobbyist, West Sussex, UK
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John Fields
Guest
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| Posted:
Thu Feb 17, 2005 9:19 pm Post subject:
Re: Turning a light on and off with momentary switch |
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On Wed, 16 Feb 2005 23:55:04 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:
| Quote: |
"John Fields" <jfields@austininstruments.com> wrote in message
news:72r7119c5t7p6vhmqsu1vopu35v65e45br@4ax.com...
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.
---
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?^)
---
Indeed :)=) One wonders what, exactly, a "marquis light" would be.
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 |
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petrus bitbyter
Guest
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| Posted:
Thu Feb 17, 2005 9:34 pm Post subject:
Re: Turning a light on and off with momentary switch |
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"Chris W" <1qazse4@cox.net> schreef in bericht
news:vJWQd.64020$jn.59932@lakeread06...
| Quote: | 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.
| Quote: |
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.
| Quote: |
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.
| Quote: | --
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
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petrus bitbyter
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Bill Bowden
Guest
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| Posted:
Fri Feb 18, 2005 3:22 am Post subject:
Re: Turning a light on and off with momentary switch |
|
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Peter Michelson wrote:
| Quote: | 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;
|
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.
The 4017 can be used for just 3 LEDs by connecting the
reset line (pin 15) to the 4th output, (pin 7).
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#4017-2.gif
-Bill |
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Bill Bowden
Guest
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| Posted:
Fri Feb 18, 2005 3:25 am Post subject:
Re: Turning a light on and off with momentary switch |
|
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Peter Michelson wrote:
| Quote: | 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;
|
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.
The 4017 can be used for just 3 LEDs by connecting the
reset line (pin 15) to the 4th output, (pin 7).
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#4017-2.gif
-Bill |
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Peter Michelson
Guest
|
| Posted:
Fri Feb 18, 2005 6:10 am Post subject:
Re: Turning a light on and off with momentary switch |
|
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"John Fields" <jfields@austininstruments.com> wrote in message
news:5vb911tha2ani58bp3au4686rm8mo5ocs0@4ax.com...
| Quote: | 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 |
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Peter Michelson
Guest
|
| Posted:
Fri Feb 18, 2005 6:10 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
"Bill Bowden" <wrongaddress@att.net> wrote in message
news:1108675337.245641.194540@o13g2000cwo.googlegroups.com...
| Quote: | 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.
| Quote: | 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). |
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Guest
|
| Posted:
Fri Feb 18, 2005 6:10 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
| Quote: | Thanks - I think that's exactly the approach that John Fields
took in his schematic (see other posting in this thread).
|
Yes, except for the extra transistors which will allow
much more current for brighter LEDs. If you hook the LEDs
directly to the 4017 with a resistor, you only get 2 or 3
milliamps. The extra transistor will get you 20 mA or more.
-Bill |
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John Fields
Guest
|
| Posted:
Fri Feb 18, 2005 10:16 pm Post subject:
Re: Turning a light on and off with momentary switch |
|
|
On Thu, 17 Feb 2005 23:11:51 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:
| Quote: |
"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 |
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John Fields
Guest
|
| Posted:
Fri Feb 18, 2005 10:39 pm Post subject:
Re: Turning a light on and off with momentary switch |
|
|
On Thu, 17 Feb 2005 23:15:16 -0500, "Peter Michelson"
<pete77r@hotmail.com> wrote:
| Quote: |
"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 |
|
| Back to top |
|
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Harold Ryan
Guest
|
| Posted:
Sat Feb 19, 2005 6:10 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
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...
| Quote: | 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 |
|
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|
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Rich Grise
Guest
|
| Posted:
Sat Feb 19, 2005 6:10 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
On Wed, 16 Feb 2005 15:19:19 -0600, Chris W wrote:
| Quote: | 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 |
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Peter Michelson
Guest
|
| Posted:
Sun Feb 20, 2005 3:06 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
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...
| Quote: | 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
|
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|
| Back to top |
|
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Peter Michelson
Guest
|
| Posted:
Sun Feb 20, 2005 3:16 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
| Quote: | Yes, except for the extra transistors which will allow
much more current for brighter LEDs. If you hook the LEDs
directly to the 4017 with a resistor, you only get 2 or 3
milliamps. The extra transistor will get you 20 mA or more.
-Bill
|
That's helpful, since I do not yet know the operating characteristics of the
LEDs that I will want to use.
Thanks,
Peter |
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| Back to top |
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Peter Michelson
Guest
|
| Posted:
Sun Feb 20, 2005 3:20 am Post subject:
Re: Turning a light on and off with momentary switch |
|
|
| Quote: | ---
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 |
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