There is a question the kids asked me about Block programming. Can anybody help with this?
When setting the “wait x seconds” in Block, is there a minimum time limit? How precisely can we control the on/off signal in Block?
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to my knowledge there is no limit to minimum time
Well, there is a minimum time, that would be 1mS. But other factors come into play, what is being turned on and off, a motor ? If so then the time to send messages to the motor will also be a factor as well as how often the motor processes those commands. I would say a practical minimum time would be 10mS (0.01 seconds).
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Thanks. for the reply.
My son is wondering how to estimate the response time of a pneumatic solenoid valve, but he is struggling with understanding the limitations of the ‘wait’ function. You are right, we also need to take into account the response time of the mechanical part itself. We may use 10ms as an approximate number for reference.
There is a practical limit. I always love these “how fast/how short” questions, As James noted it is really a “it depends” answer. For @VEX8181K this is a great chance for your roboteers to do experimentation on what they are trying to do.
I’ll bet that if you do a loop with the LED with on-wait-off loop that it will be just a few milliseconds until you can detect a flicker, since the human eye is pretty sensitive.
But if the loop is on-wait-off with a motor, that it won’t move, or if you stick a wheel on it and get it up to speed then try to do the flicker, it won’t really slow, the roboteers will learn lots about inertia.
Report back on their findings (and make sure it’s in their notebook).
This is what I love about robotics, it’s where “theory meets practice”.
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The IQ pneumatic solenoid actuates in about 150mS, the air cylinder will then take more time, so perhaps 300mS until all mechanical movement has finished, but it could be longer, depends on the mechanism.
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The LED flashing experiment is a fantastic idea for testing response time related to the “electric switch.” I will encourage kids to work on a program that loops in different wait time intervals for LED flashing. I also plan to help them take a short video using the slow motion mode on an iPhone (approximately 240 FPS). Let’s see what they may discover!
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Kids created a piece of code to change a green LED to red and switch it back to green with various wait times. They used iPad to capture the flicker with wait times as short as 0.00001 seconds. For the human eyes, flicker with a wait time of 0.001 seconds is noticeable. The electrical delay seems negligible, and they will focus on mechanical response time for the pneumatic control.
They will summarize this experiment as a page in the notebook for their project.
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