Momentary Gate Switch

[shoeInsertsForDummies]

I will try my best to explain what im trying to accomplish. I'm using a
momentary switch to trigger a solenoid valve to release air pressure in
a home made potato gun. I have found that you can get multiple bursts
out of the gun if you flick the momentary switch very quickly. The
pressure decrease is small enough to shoot multiple objects without
re-pumping which would be very convienient and much more efficient then
exhausting all the excess pressurized air.

I am looking to make a circuit that would create a square wave for
about a tenth of a second when the momentary button is pushed. The
input is 18v in a series of two 9v batteries. The output should also
maintain the 18v difference.

I'm not sure what to call the switch im trying to make and am not sure
if it is in the correct group, however any information you could throw
my way would help considerably.

thanks,
dave

birmingham, al

 

[[email protected]]

I will try my best to explain what im trying to accomplish. I'm using a
momentary switch to trigger a solenoid valve to release air pressure in
a home made potato gun. I have found that you can get multiple bursts
out of the gun if you flick the momentary switch very quickly. The
pressure decrease is small enough to shoot multiple objects without
re-pumping which would be very convienient and much more efficient then
exhausting all the excess pressurized air.

I am looking to make a circuit that would create a square wave for
about a tenth of a second when the momentary button is pushed. The
input is 18v in a series of two 9v batteries. The output should also
maintain the 18v difference.

I'm not sure what to call the switch im trying to make and am not sure
if it is in the correct group, however any information you could throw
my way would help considerably.

It's usually called a pulse generator or one shot. From your
description of your application I assume you don't really want a square
"wave" but want a square "pulse" instead. If that's the case a simple
555 timer can be used to create a one shot circuit where the output
pulse width is constant regardless of the input pulse width:

http://www.uoguelph.ca/~antoon/circ/monovib.htm

 

[shoeInsertsForDummies]

Excellent.
The equation is t = R1*C1, so im assuming that a 100k resistor and a
1uF cap would create a pulse of .1 seconds. Is that correct?

thanks,
dave

 

[Fred Bloggs]

I will try my best to explain what im trying to accomplish. I'm using a

momentary switch to trigger a solenoid valve to release air pressure in
a home made potato gun. I have found that you can get multiple bursts
out of the gun if you flick the momentary switch very quickly. The
pressure decrease is small enough to shoot multiple objects without
re-pumping which would be very convienient and much more efficient then
exhausting all the excess pressurized air.

I am looking to make a circuit that would create a square wave for
about a tenth of a second when the momentary button is pushed. The
input is 18v in a series of two 9v batteries. The output should also
maintain the 18v difference.

I'm not sure what to call the switch im trying to make and am not sure
if it is in the correct group, however any information you could throw
my way would help considerably.

It's called a "one-shot" and we would need to know how the resistance of
the solenoid to pin down an exact circuit, but it may be something along
the lines shown below made from Radio Shack components. The other
circuit in the web link is a fiction- doesn't work.
View in a fixed-width font such as Courier.

..
..
..
.. |9V 1N4001
.. .---------------------------||----------------|>|---+----+---.
.. | | | S |
.. | 1N4001 1N4001- S |
.. +--|>|-----+----------+----+-----------. ^ S |
.. | | | | 0.1U | | S |
.. | | [1K] === | | | |+
.. | | | +--[1M]-----+ | | ===
.. | | | | | 555 | | 100U
.. | | | | ---------- | | 35WVDC
.. | | | | | V+/RST | | | |
.. | | .-+ | | CNT|-N/C '----+ |
.. ---9V .---+ | | +-[1K]-|DIS | | |
.. - | |+ SW o | | | | d| |
.. | | === -| | '------|THRESH | IRF510|- |
.. | | |1U o | | OUT|---+-----|< |
.. | [100K] |16WVDC | '-----------|TRIG | | |- |
.. | | | .----+ | | | s| |
.. | | | | | | GND | [10K] '---+
.. | | | [10K] === ---------- | |
.. | | | | |0.1U | | [220]
.. | / | | | | | | |
.. '-o o--+---+---+----+------------------+---------+-----------'
.. on/off
..
..
..
..
..
..

 

[Fred Bloggs]

I will try my best to explain what im trying to accomplish. I'm using a
momentary switch to trigger a solenoid valve to release air pressure in
a home made potato gun. I have found that you can get multiple bursts
out of the gun if you flick the momentary switch very quickly. The
pressure decrease is small enough to shoot multiple objects without
re-pumping which would be very convienient and much more efficient then
exhausting all the excess pressurized air.

I am looking to make a circuit that would create a square wave for
about a tenth of a second when the momentary button is pushed. The
input is 18v in a series of two 9v batteries. The output should also
maintain the 18v difference.

I'm not sure what to call the switch im trying to make and am not sure
if it is in the correct group, however any information you could throw
my way would help considerably.

It would be better to make the ON/OFF switch a SPDT to discharge the
solenoid capacitor in OFF, and add a DIScharge momentary to either use
conventionally or blow the tank before storage:
View in a fixed-width font such as Courier.

..
..
..
.. |9V 1N4001
.. .---------------------------||----------------|>|---+----+---+---.
.. | | | S | |
.. | 1N4001 1N4001- S | |
.. +--|>|-----+----------+----+-----------. ^ S | |
.. | | | | 0.1U | | S | |
.. | | [1K] === | | | |+ |
.. | | | +--[1M]-----+ | | === |
.. | | | | | 555 | | 100U |
.. | | | | ---------- | | 35WVDC|
.. | | | | | V+/RST | | | | |
.. | | .-+ | | CNT|-N/C '--+-+ | |
.. ---9V .---+ PULSE| | +-[1K]-|DIS | | | | |
.. - | |+ SW o | | | |IRF510 d| | | |
.. | | === -| | '------|THRESH | |- | | |
.. | | |1U o | | OUT|---+---|< | | |
.. | [100K] |16WVDC | '-----------|TRIG | | |- | | |
.. | | | .----+ | | | s| | | |
.. | | | | | | GND | [10K] '-----+ |
.. | | | [10K] === ---------- | | | |
.. | on | | | |0.1U | | | [220] |
.. +--o | | | | | | | | |
.. | o-+---+---+----+------------------+---------+-----------' |
.. | / | |
.. | o-------------------------------------------------------------'
.. | off DIS |
.. | SW o
.. | -|
.. | o
.. | |
.. '--------------------------------------------------------'
..

 

[Fred Bloggs]

I will try my best to explain what im trying to accomplish. I'm using a
momentary switch to trigger a solenoid valve to release air pressure in
a home made potato gun. I have found that you can get multiple bursts
out of the gun if you flick the momentary switch very quickly. The
pressure decrease is small enough to shoot multiple objects without
re-pumping which would be very convienient and much more efficient then
exhausting all the excess pressurized air.

I am looking to make a circuit that would create a square wave for
about a tenth of a second when the momentary button is pushed. The
input is 18v in a series of two 9v batteries. The output should also
maintain the 18v difference.

I'm not sure what to call the switch im trying to make and am not sure
if it is in the correct group, however any information you could throw
my way would help considerably.

It would be better to make the ON/OFF switch a SPDT to discharge the
solenoid capacitor in OFF, and add a DIScharge momentary to either use
conventionally or blow the tank before storage:
View in a fixed-width font such as Courier.

.
.
.
. |9V 1N4001
. .---------------------------||----------------|>|---+----+---+---.
. | | | S | |
. | 1N4001 1N4001- S | |
. +--|>|-----+----------+----+-----------. ^ S | |
. | | | | 0.1U | | S | |
. | | [1K] === | | | |+ |
. | | | +--[1M]-----+ | | === |
. | | | | | 555 | | 100U |
. | | | | ---------- | | 35WVDC|
. | | | | | V+/RST | | | | |
. | | .-+ | | CNT|-N/C '--+-+ | |
. ---9V .---+ PULSE| | +-[1K]-|DIS | | | | |
. - | |+ SW o | | | |IRF510 d| | | |
. | | === -| | '------|THRESH | |- | | |
. | | |1U o | | OUT|---+---|< | | |
. | [100K] |16WVDC | '-----------|TRIG | | |- | | |
. | | | .----+ | | | s| | | |
. | | | | | | GND | [10K] '-----+ |
. | | | [10K] === ---------- | | | |
. | on | | | |0.1U | | | [220] |
. +--o | | | | | | | | |
. | o-+---+---+----+------------------+---------+-----------' |
. | / | |
. | o-------------------------------------------------------------'
. | off DIS |
. | SW o
. | -|
. | o
. | |
. '--------------------------------------------------------'
.

This connection is more logical- when the ON/OFF is OFF it can't do
anything, you have to be in ON position to pulse or discharge:
View in a fixed-width font such as Courier.

..
..
..
.. |9V 1N4001
.. .---------------------------||----------------|>|---+----+---+---.
.. | | | S | |
.. | 1N4001 1N4001- S | |
.. +--|>|-----+----------+----+-----------. ^ S | |
.. | | | | 0.1U | | S | |
.. | | [1K] === | | | |+ |
.. | | | +--[1M]-----+ | | === |
.. | | | | | 555 | | 100U |
.. | | | | ---------- | | 35WVDC|
.. | | | | | V+/RST | | | | |
.. | | .-+ | | CNT|-N/C '--+-+ | |
.. ---9V .---+ PULSE| | +-[1K]-|DIS | | | | |
.. - | |+ SW o | | | |IRF510 d| | | |
.. | | === -| | '------|THRESH | |- | | |
.. | | |1U o | | OUT|---+---|< | | |
.. | [100K] |16WVDC | '-----------|TRIG | | |- | | |
.. | | | .----+ | | | s| | | |
.. | | | | | | GND | [10K] '-----+ |
.. | | | [10K] === ---------- | | | |
.. | on | | | |0.1U | | | [220] |
.. '--o | | | | | | | | |
.. o-+---+---+----+------------------+---------+-----------' |
.. / | | |
.. o-------------------------------------------------------------'
.. off | DIS |
.. | SW o
.. | -|
.. | o
.. | |
.. '-----------------'
..

 

[Robert Scott]

Excellent.
The equation is t = R1*C1, so im assuming that a 100k resistor and a
1uF cap would create a pulse of .1 seconds. Is that correct?

Almost. You have to think about what is happening in an analog sense.
The time you get from R1*C1 is the time it takes the C1 to discharge
into R1 down to the level of .3679 of what it was to start with. If
you start with C1 charged to the logic level of +5 volts and if you
are discharging it into R1 and if you are watching the voltage on C1
with a comparator that has a threshold set to 1.839 volts, then the
comparator will flip .1 seconds after the discharge begins. If the
comparator threshold is set to some other voltage, then the switching
time will change accordingly.


-Robert Scott
Ypsilanti, Michigan