toogr82h8 said:
Hello Everyone,
Okay so I am new to the engineering stuff and am starting off with some basic ideas. I won't get into all of them but I had a question.
I want to build a push button flag pole. I am talking something maybe 2 feet tall that would raise and lower one of those small scall flags. It is novelty but I am trying to learn some basic stuff before I start going bigger.
I know I could build a one way pulley system but I don't know how to make the thing stop at a certain point and stuff.
There are a number of ways to do this. A basic approach would be to use some SR flip-flops to control the power to a motor which drives the pulley system. Stops on the rope would trigger buttons to turn off the motor when the flag reaches the desired location.
Driving the flag in one direction is fairly easy because it only involves one set and one reset (on and off). Getting it to go the other way is a little more complicated because you need to reverse the power to the motor. You should get familiar with the flipflop and h-bridge before attempting that.
Another way to get the flag going both directions would be to use a motor that runs only one way but a drive train that is reversible. The electronics would be similar as far as tracking where the flag needs to go, but you might not need the h-bridge driver.
Check out the wikipedia page on flip-flops and on h-bridge drivers. The h-bridge is useful because it has two inputs that give you 3 states, forward, backward and idle (actually there are 4 states, but the 4th one is usually 'self-destruct', so you generally want to avoid that one). The flip-flops are useful because they will latch on or off after a momentary button press. The first button press can turn on the output, and the second button press would come from a limit switch installed on the rope which turns off the output. During the time between the two button presses the motor runs on it's own with no buttons being held.
Once you understand how they work you have to analyze the logic to see how to get the states that you want.
Thanks for the help.
Feel free to ask me about anything relating to old chevy motors!
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