flip-flop question

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

 

[Lord Garth]

<razorboy@gmail.com> wrote in message
news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

Why not build an astable multivibrator with the 555? You will then get
a constant stream of ticks.


Or post your schematic on alt.binaries.schematics.electronic

 

On Mar 24, 2:07 pm, "Lord Garth" <lga...@tantalus.net> wrote:

razor...@gmail.com> wrote in message

news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

Why not build an astable multivibrator with the 555?  You will then get
a constant stream of ticks.

Or post your schematic on alt.binaries.schematics.electronic

I need to be able to start/stop the ticks. From what I've seen you
can't really do that with astable. Am I correct?

 

[Lord Garth]

<razorboy@gmail.com> wrote in message
news:7fd7ea63-3d0b-4835-ac24-e8e655bb148c@i12g2000prf.googlegroups.com...
On Mar 24, 2:07 pm, "Lord Garth" <lga...@tantalus.net> wrote:

razor...@gmail.com> wrote in message

news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

Why not build an astable multivibrator with the 555? You will then get
a constant stream of ticks.

Or post your schematic on alt.binaries.schematics.electronic

I need to be able to start/stop the ticks. From what I've seen you
can't really do that with astable. Am I correct?

No, you can drive the reset input and stop the oscillator with a simple
toggle switch.

 

[Bob Monsen]

<razorboy@gmail.com> wrote in message
news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

If I get you, I think you want to enable/disable the 555 using the same
pushbutton, is that right?

If so, you can use a couple of inverters (cmos 4049 perhaps) along with a
normally open push button and and resistors/capacitors to do this.

.-----------------------------------------.
| |
| |\ ___ |\ ___ |
'----| >O-|___|--o----| >O----o---|___|---'
|/ 100k | |/ | 100k
| |
4049 | 4049 .-.
| | | 330k
| | |
| T '-'
| --- |
'-----o o----o
|
--- 1uF
---
|
|
===
GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

The pushbutton is normally open. The capacitor is charged to the output of
the right inverter. When you push the button, it changes the value of the
input of the right inverter, causing it to change its output. This is
independent of the starting state.

Use the real output (not the output after the 100k resistor) to drive the
reset of the 555.

Regards,
Bob Monsen

 

On Mar 24, 2:41 pm, "Lord Garth" <lga...@tantalus.net> wrote:

razor...@gmail.com> wrote in message

news:7fd7ea63-3d0b-4835-ac24-e8e655bb148c@i12g2000prf.googlegroups.com...
On Mar 24, 2:07 pm, "Lord Garth" <lga...@tantalus.net> wrote:





razor...@gmail.com> wrote in message

news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

Why not build an astable multivibrator with the 555? You will then get
a constant stream of ticks.

Or post your schematic on alt.binaries.schematics.electronic

I need to be able to start/stop the ticks. From what I've seen you
can't really do that with astable. Am I correct?

No, you can drive the reset input and stop the oscillator with a simple
toggle switch.- Hide quoted text -

- Show quoted text -

The only constraint I have for this circuit is the momentary switch
for user input.

 

On Mar 24, 3:15 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:

razor...@gmail.com> wrote in message

news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

If I get you, I think you want to enable/disable the 555 using the same
pushbutton, is that right?

If so, you can use a couple of inverters (cmos 4049 perhaps) along with a
normally open push button and and resistors/capacitors to do this.

    .-----------------------------------------.
    |                                         |
    |    |\    ___        |\           ___    |
    '----| >O-|___|--o----| >O----o---|___|---'
         |/    100k  |    |/      |    100k
                     |            |
         4049        |    4049   .-.
                     |           | | 330k
                     |           | |
                     |      T    '-'
                     |     ---    |
                     '-----o o----o
                                  |
                                 --- 1uF
                                 ---
                                  |
                                  |
                                 ==>                                  GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

The pushbutton is normally open. The capacitor is charged to the output of
the right inverter. When you push the button, it changes the value of the
input of the right inverter, causing it to change its output. This is
independent of the starting state.

Use the real output (not the output after the 100k resistor) to drive the
reset of the 555.

Regards,
 Bob Monsen

That looks great, but where do I put the trigger and reset lines from
the 555?

 

[Lord Garth]

<razorboy@gmail.com> wrote in message
news:808f70a7-69e9-42fe-acd6-0cc0cec5fe10@u10g2000prn.googlegroups.com...

<snip>

The only constraint I have for this circuit is the momentary switch
for user input.

Okay, a T flip flop with a debounced push button switch as its clock
input. The output goes to the reset input of the 555.

You can form a T flip flop if you take a D flip flop and connect the Q*
output back to the D input.

 

On Mar 24, 4:46 pm, "Lord Garth" <lga...@tantalus.net> wrote:

razor...@gmail.com> wrote in message

news:808f70a7-69e9-42fe-acd6-0cc0cec5fe10@u10g2000prn.googlegroups.com...

snip

The only constraint I have for this circuit is the momentary switch
for user input.

Okay, a T flip flop with a debounced push button switch as its clock
input.  The output goes to the reset input of the 555.

You can form a T flip flop if you take a D flip flop and connect the Q*
output back to the D input.

What do I connect the trigger input of the 555 to? The D input of the
flip-flop?

 

[Bob Monsen]

<razorboy@gmail.com> wrote in message
news:44d3d0bc-ff2e-4592-8c30-4753d84d44c7@s37g2000prg.googlegroups.com...
On Mar 24, 3:15 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:

razor...@gmail.com> wrote in message

news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

If I get you, I think you want to enable/disable the 555 using the same
pushbutton, is that right?

If so, you can use a couple of inverters (cmos 4049 perhaps) along with a
normally open push button and and resistors/capacitors to do this.

.-----------------------------------------.
| |
| |\ ___ |\ ___ |
'----| >O-|___|--o----| >O----o---|___|---'
|/ 100k | |/ | 100k
| |
4049 | 4049 .-.
| | | 330k
| | |
| T '-'
| --- |
'-----o o----o
|
--- 1uF
---
|
|
===
GND
(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)

The pushbutton is normally open. The capacitor is charged to the output of
the right inverter. When you push the button, it changes the value of the
input of the right inverter, causing it to change its output. This is
independent of the starting state.

Use the real output (not the output after the 100k resistor) to drive the
reset of the 555.

Regards,
Bob Monsen

That looks great, but where do I put the trigger and reset lines from
the 555?


You set up the 555 as an astable multivibrator, and let it free run. You
connect this to the reset pin of the 555. When it is "high" output, the 555
will output pulses for you. When it is "low" output, the 555 will wait for a
"high" output, and output no pulses.

The typical setup for an astable is to have two resistors and a capacitor.
Connect the resistors in series with the capacitor between the voltage
supply and ground. Connect the discharge pin between the resistors, and both
the 'trigger' and 'threshold' to the cap:

-----------o-----------------.
Vcc(12v) | |
| .-.
| | | R1
| | |
| __ '-'
'---o| |o-----. |
.----o| |o-----)--o
output ----)----o| |o---. | |
reset ----)----o|__|o- | | .-.
| | | | | R2
| | | | |
| | | '-'
| | | |
'-------------o-)--o
| |
| --- C1
| ---
| |
GND | |
---------------------------o--'

1/f = discharge time through R2 +
charge time through R1 + R2

Discharge through R2 is .693 * R2 * C
Charge through R1 and R2 is .693 * (R1 + R2) * C

So, f = 1.44/(R1*C + 2*R2*C)
and d = 100 * R2 / (R1 + R2)

(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Regards,
Bob Monsen

 

[Lord Garth]

<razorboy@gmail.com> wrote in message
news:9f1297c3-b1c0-4ff3-8c7d-2e83f8f13f8a@e6g2000prf.googlegroups.com...
On Mar 24, 4:46 pm, "Lord Garth" <lga...@tantalus.net> wrote:

razor...@gmail.com> wrote in message

news:808f70a7-69e9-42fe-acd6-0cc0cec5fe10@u10g2000prn.googlegroups.com...

snip

The only constraint I have for this circuit is the momentary switch
for user input.

Okay, a T flip flop with a debounced push button switch as its clock
input. The output goes to the reset input of the 555.

You can form a T flip flop if you take a D flip flop and connect the Q*
output back to the D input.

What do I connect the trigger input of the 555 to? The D input of the
flip-flop?

It's an astable multivibrator...build that first, get it oscillating then
work on holding the reset active to stop it.

 

On 3ÔÂ25ČŐ, ÉĎÎç4Ęą27ˇÖ, razor...@gmail.com wrote:

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

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[John Fields]

On Mon, 24 Mar 2008 21:07:08 GMT, "Lord Garth" <lgarth@tantalus.net>
wrote:

razorboy@gmail.com> wrote in message
news:98e1cf07-f360-443a-bfee-e19b63d50db7@s8g2000prg.googlegroups.com...
I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

---
Yes. Assuming you're talking about digital inputs and outputs, the
whole thing can be done with a dual "D" type flip-flop and three NAND
gates. View in Courier:

C1
Vcc>-+-[100nF]-+--------+-------+
| | |R1 |
| | [1MR] | IN1
+---+ | | | | 4011
| | | U1a GND | U1b +-B U2a
S1| O | +--+--+ +--+--+ NAND Y--+
| O +--|D S Q|-----+----|> S Q|------A |
| | | | | _| +--A
+------|> R | | +-|D R Q|-+ NAND Y-->OUT
| +--+--+ | | +--+--+ | +--B U2c
[10K] 4013| | +----|----+----B |
|R2 +--[Rt]--+ | NAND Y--+
| | | | +-A U2b
| +-[CR1>]-+ | |
| [Ct] | |
| | | IN2
GND>-+---------+----------------+


Select Rt and Ct for a time constant longer than the press-release
cycle of S1.

On power-up, the S(et) inputs of U1a and B are pulled high momentarily
by C1 and R1, forcing U1a-Q high, U1b-Q high and U1b-Q\ low.

Since the signal on U1a-S will stay high longer than the edge from
U1a-Q, U1b-Q will remain high and U1b-Q\ will remain low until U1a
times out and S1 is pressed.

U2a, b, and c comprise a 2-to-1 multiplexer, and with U1a high and
U1b low, the logic signal appearing on IN1 will appear on OUT until S1
is pressed.

When S1 is pressed, U1a-Q will go high and will toggle the outputs of
U1b, now causing the signal on IN2 to appear on OUT.

When U1a-Q goes high it also starts charging Ct through Rt, and when
the voltage on U1a-R gets high enough it will reset U1a and discharge
Ct quickly through CR1, which can be any common signal diode, say a
1N4148.

After that, every time S1 is pressed the cycle will begin anew and
the signal on OUT will alternate between the signal on IN1 and IN2.

If you decide to build this circuit, be sure to connect the inputs of
the unused NAND to either Vcc or GND.

 

[John Fields]

On Tue, 25 Mar 2008 09:09:06 -0500, John Fields
<jfields@austininstruments.com> wrote:

C1
Vcc>-+-[100nF]-+--------+-------+
| | |R1 |
| | [1MR] | IN1
+---+ | | | | 4011
| | | U1a GND | U1b +-B U2a
S1| O | +--+--+ +--+--+ NAND Y--+
| O +--|D S Q|-----+----|> S Q|------A |
| | | | | _| +--A
+------|> R | | +-|D R Q|-+ NAND Y-->OUT
| +--+--+ | | +--+--+ | +--B U2c
[10K] 4013| | +----|----+----B |
|R2 +--[Rt]--+ | NAND Y--+
| | | | +-A U2b
| +-[CR1>]-+ | |
| [Ct] | |
| | | IN2
GND>-+---------+----------------+


Select Rt and Ct for a time constant longer than the press-release
cycle of S1.

On power-up, the S(et) inputs of U1a and B are pulled high momentarily
by C1 and R1, forcing U1a-Q high, U1b-Q high and U1b-Q\ low.

Since the signal on U1a-S will stay high longer than the edge from
U1a-Q, U1b-Q will remain high and U1b-Q\ will remain low until U1a
times out and S1 is pressed.

U2a, b, and c comprise a 2-to-1 multiplexer, and with U1a high and
U1b low, the logic signal appearing on IN1 will appear on OUT until S1
is pressed.

When S1 is pressed, U1a-Q will go high and will toggle the outputs of
U1b, now causing the signal on IN2 to appear on OUT.

When U1a-Q goes high it also starts charging Ct through Rt, and when
the voltage on U1a-R gets high enough it will reset U1a and discharge
Ct quickly through CR1, which can be any common signal diode, say a
1N4148.

After that, every time S1 is pressed the cycle will begin anew and
the signal on OUT will alternate between the signal on IN1 and IN2.

If you decide to build this circuit, be sure to connect the inputs of
the unused NAND to either Vcc or GND.

---
Version 4
SHEET 1 2244 800
WIRE 64 -272 -32 -272
WIRE 224 -272 128 -272
WIRE 352 -272 224 -272
WIRE 880 -272 352 -272
WIRE 1024 -256 752 -256
WIRE 1280 -240 1120 -240
WIRE 352 -224 352 -272
WIRE 880 -224 880 -272
WIRE 1440 -192 1344 -192
WIRE -32 -176 -32 -272
WIRE 272 -176 -32 -176
WIRE 528 -176 432 -176
WIRE 608 -176 528 -176
WIRE 704 -176 608 -176
WIRE 752 -176 752 -256
WIRE 800 -176 752 -176
WIRE 1280 -176 960 -176
WIRE 1536 -144 1504 -144
WIRE 272 -128 96 -128
WIRE 480 -128 448 -128
WIRE 528 -128 528 -176
WIRE 608 -128 608 -176
WIRE 704 -128 704 -176
WIRE 800 -128 704 -128
WIRE 1024 -128 1024 -256
WIRE 1024 -128 976 -128
WIRE 1280 -128 1024 -128
WIRE 1440 -128 1392 -128
WIRE 1392 -112 1392 -128
WIRE 1392 -112 1344 -112
WIRE 1280 -64 1248 -64
WIRE 352 -16 352 -80
WIRE 528 -16 528 -64
WIRE 528 -16 352 -16
WIRE 608 -16 608 -48
WIRE 608 -16 528 -16
WIRE 1536 0 1536 -144
WIRE -32 16 -32 -176
WIRE 96 16 96 -128
WIRE 224 16 224 -272
WIRE 480 16 480 -128
WIRE 1120 16 1120 -240
WIRE 1248 16 1248 -64
WIRE 608 32 608 -16
WIRE -32 144 -32 96
WIRE 96 144 96 96
WIRE 96 144 -32 144
WIRE 224 144 224 96
WIRE 224 144 96 144
WIRE 480 144 480 96
WIRE 480 144 224 144
WIRE 608 144 608 96
WIRE 608 144 480 144
WIRE 880 144 880 -80
WIRE 880 144 608 144
WIRE 1120 144 1120 96
WIRE 1120 144 880 144
WIRE 1248 144 1248 96
WIRE 1248 144 1120 144
WIRE 1536 144 1536 80
WIRE 1536 144 1248 144
WIRE -32 176 -32 144
FLAG -32 176 0
SYMBOL voltage 96 0 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 1e-6 1e-6 1 2)
SYMATTR InstName V2
SYMBOL voltage -32 0 R0
WINDOW 3 24 104 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value 5
SYMATTR InstName V1
SYMBOL res 592 -144 R0
SYMATTR InstName R1
SYMATTR Value 1e6
SYMBOL cap 592 32 R0
SYMATTR InstName C1
SYMATTR Value 1e-6
SYMBOL Digital\\dflop 352 -224 R0
SYMATTR InstName A1
SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v
SYMBOL res 464 0 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL diode 544 -64 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL Digital\\dflop 880 -224 R0
SYMATTR InstName A2
SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v
SYMBOL res 208 0 R0
SYMATTR InstName R3
SYMATTR Value 1e6
SYMBOL cap 128 -288 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C2
SYMATTR Value 1e-8
SYMBOL Digital\\and 1312 -272 R0
SYMATTR InstName A3
SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v
SYMBOL Digital\\and 1472 -224 R0
SYMATTR InstName A5
SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v
SYMBOL Digital\\and 1312 -32 M180
SYMATTR InstName A6
SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v
SYMBOL res 1520 -16 R0
SYMATTR InstName R4
SYMATTR Value 10k
SYMBOL voltage 1248 0 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 1e-6 1e-6 .25 .5)
SYMATTR InstName V3
SYMBOL voltage 1120 0 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 1e-6 1e-6 .1 .2)
SYMATTR InstName V4
TEXT 48 192 Left 0 !.tran 5
TEXT 48 232 Left 0 !.option noopiter

 

On 3ÔÂ25ČŐ, ÉĎÎç4Ęą27ˇÖ, razor...@gmail.com wrote:

I'm designing a circuit and I need something to switch between two
inputs. I don't have very much experience, but I think a certain type
of flip-flop will do this?

I'm using a 555 (as a monostable vibrator), and I need the same
momentary push button to toggle between the trigger and the reset
lines. Basically it's like a metronome with a single start/stop
switch.

Can I do this with a flip-flop?

Do you want access to China's massive pool of electronic
manufacturers... but lack the time to contact suppliers, negotiate
contracts, arrange shipping or monitor product quality? Don't worry -
Let seriouswholesale deal with all that for you.

*Check out the huge range of Gadgets, MP3 / MP4 Players, Car DVD /
Audio, and Computer Accessories now by visiting the online wholesale
catalog at seriouswholesale. com You'll have peace of mind thanks to
the seriouswholesale Quality Control, 12-month Warranty on all
products, and easy secure payment by credit card through Paypal.

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