Hello,
I am volunteering at a local children's science center to help them create a new exhibit. It will consist of a number of devices that are "solar powered" (really light-actuated). One of the devices will be a pneumatic rocket, similar to what is described in this article of Make Magazine . Ours will be actuated by shining a light on a solar cell instead of with a hand-held switch. Also, we have a mechanism where the rocket launches, and falls back onto the launch tube for re-launch.
A simple way to accomplish this would be to connect a solar cell across the input of a relay, and use the relay to switch power to the solenoid valve. Ideally, you would shine a light on the cell, the valve would open, and you would remove the light as soon as the rocket exits the launch tube. The rocket would fly up, and fall back onto the launch tube. More likely, children will keep the light on the cell, keeping the valve open, wasting air pressure, and preventing the rocket from engaging with the launch tube.
My first thought was to create a mechanism where the rocket itself closed a switch, which would enable activation. However, it may be difficult to make this reliable.
Then I thought I could just create a timer circuit with an "on" time corresponding to the time it takes for the rocket to exit the launch tube (say 1 second) and an "off" time corresponding to the time it takes from launch till the rocket is back on the tube (say 10 seconds).
So I merged the extended duty cycle astable 555 circuit and the reset input circuit, with the reset input connected to the output of a comparator, which detects an increase in light on the solar cell. This would work perfectly if the user kept the light on the cell. The problem is if they shine light on the cell for a brief period of time, take it off, and then shine it on the cell again. The valve would be re-activated each time, and the "on" and "off" times set by the 555 would not be enforced.
So I looked at the trigger circuit. This enforces the "on" and "off" time, but it forces the user to remove and reapply the light to re-trigger. And, the user could re-trigger before the "off" time has passed.
So I'm a bit stumped, and I'm hoping someone here will be able to help. Here are the parameters:
I have attached my working schematic.
Thanks in advance,
Jim
I am volunteering at a local children's science center to help them create a new exhibit. It will consist of a number of devices that are "solar powered" (really light-actuated). One of the devices will be a pneumatic rocket, similar to what is described in this article of Make Magazine . Ours will be actuated by shining a light on a solar cell instead of with a hand-held switch. Also, we have a mechanism where the rocket launches, and falls back onto the launch tube for re-launch.
A simple way to accomplish this would be to connect a solar cell across the input of a relay, and use the relay to switch power to the solenoid valve. Ideally, you would shine a light on the cell, the valve would open, and you would remove the light as soon as the rocket exits the launch tube. The rocket would fly up, and fall back onto the launch tube. More likely, children will keep the light on the cell, keeping the valve open, wasting air pressure, and preventing the rocket from engaging with the launch tube.
My first thought was to create a mechanism where the rocket itself closed a switch, which would enable activation. However, it may be difficult to make this reliable.
Then I thought I could just create a timer circuit with an "on" time corresponding to the time it takes for the rocket to exit the launch tube (say 1 second) and an "off" time corresponding to the time it takes from launch till the rocket is back on the tube (say 10 seconds).
So I merged the extended duty cycle astable 555 circuit and the reset input circuit, with the reset input connected to the output of a comparator, which detects an increase in light on the solar cell. This would work perfectly if the user kept the light on the cell. The problem is if they shine light on the cell for a brief period of time, take it off, and then shine it on the cell again. The valve would be re-activated each time, and the "on" and "off" times set by the 555 would not be enforced.
So I looked at the trigger circuit. This enforces the "on" and "off" time, but it forces the user to remove and reapply the light to re-trigger. And, the user could re-trigger before the "off" time has passed.
So I'm a bit stumped, and I'm hoping someone here will be able to help. Here are the parameters:
- strict "on" and "off" time is enforced (roughly 1 second and 10 seconds respectively)
- if the user keeps the light on the cell, it will act like an astable, and keep launching the rocket
- if the user removes and reapplies the light before the "on" and "off" time has passed, nothing will happen.
- if the user removes and reapplies the light after "on" and "off" time has passed, the rocket will launch.
- use few new components if possible
I have attached my working schematic.
Thanks in advance,
Jim
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