Exo Arm Work Night
Date: 5.19.17
Location: Logan HS
Goal: Connect and test the timing circuit and fix the issue we are having with the linear actuator circuit not supplying the actuator with 12 VDC and stalling out.
Time: 3.5 hours
Students: Grant and Ben
Tonight we wanted to test out both the timer circuit and get our linear actuator running the way it was supposed to. We only got one of these done (timer circuit) but we did find the problem with the actuator.
The actuator circuit is driven with a half H-Bridge. It really is a very simple design that started out complex but Grant broke it down in a very nice solution. The problem was the H-Bridge will max out at 1 Amp. The linear actuator can draw up to 3 amps continuous and a 10 amp peak. So we had a driver for our linear actuator that was not supplying enough current.
The best solution we had was to insert in a Pololu 18v15 Motor Driver I had and try to wire it into the switch. We worked on the logic for while and hooked the system up. It would drive the actuator but not the way we wanted it to. We tried another configuration and accidentally connected a 5 V input to a 12 VDC connection and fried the chip. This happened at about 7:30 at night and we were all getting pretty wore out from trying to solve the problem.
We had a lot planned for the short time we had and that probably cost us one of our motor drivers. When working into the evening, everyone is tired and we were not as alert as we should have been in checking out faults when wiring in a new motor controller.
The timer circuit on the other hand worked nicely. The whole purpose of this circuit is to allow the operator time to get both his/her hands on the grinder before it starts up for safety reasons. The potentiometer allows us to adjust the time delay to whatever we want it to be. Right now it is at 3 sec. The switch and e-stop will get placed in series over the weekend to complete that circuit.
I ordered another motor controller so we can install it next week and hopefully get the linear actuator working.
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| Mr. Foye looking over a Ben's soldering job. |
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| Looking down at the control box. |
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| Grant working on some components. |
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| Testing out the wiring of the receptacles. |
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| If you look closely at the chip where the pen is pointing you will see the burned out chip. Look for a white scorch mark. |
Ben successfully testing the delay in the grinder turning on.
Grant working on parts in the control box.
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