Power Tool Drag Racing! September 25th Entries open.

**geeza** · 22nd September 2011, 22:28

Good luck to all of you competeing at the weekend, have fun.

**blazerbotics** · 22nd September 2011, 22:41

bloody hell Graeme, there's more engineering your screen bracket then there is in the whole of mine! Had a quick test run on mine today, with just 2 engines (nobody else about, so didnt fancy risking it on 4) got to 31mph fairly quickly, and still had more to give, think it should easily hit 40mph within the 100m. One of the spark plugs is creating aload of EMF and causing the servos to not respond, so need to swap that out tommorrow. Don't want to test it too much as the belts are stretching and im running out of adjustment to take up the slack!

**mark_m** · 22nd September 2011, 23:17

Still got loads to do on ours. With a bit of luck we'll be out testing tomorrow afternoon.

Damn 2 strokes.
We've also had issues with emf and servos. Now looking for somewhere we can pick up new spark plugs from

**blazerbotics** · 22nd September 2011, 23:29

lookin' good, what are you using to control the servos?

**mark_m** · 23rd September 2011, 06:37

Originally it was: potentiometer ->(analogue voltage) -> arduino ->(i2c) -> Servo control pic -> (pwm) -> servo. This works fine in the garage but when an engine is running it frequently cuts out. In some bench testing we found the pic was sensitive to noise (even the noise generated by servos was enough for it to lock up sometimes). Adding extra capacitance on the power lines appeared to cure that.
We're now going to try: potentiometer ->(analogue voltage) -> arduino -> (pwm) -> servo. to reduce the variables.

I think bolt lightning was using an Arduino to control there engines, so I think that should be tough enough to survive working near an engine. I'm not sure if they were using servos or something else though.

**robotwars** · 23rd September 2011, 09:05

why do you need to use servos ?

John

**blazerbotics** · 23rd September 2011, 10:26

Im using a standard off the shelf servo tester board (the one from Technobots). Im using servos as it was easier than trying to do it all with direct linkages/cables , i did that last year, but wasn't great, could be done but too much hassle.

**robotwars** · 23rd September 2011, 10:29

i see, i thought maybe there was a rule or something !!

**blazerbotics** · 23rd September 2011, 18:09

hmm, wish i had made a electric powered one now, as the van sticks of petrol! Not looking forward to the 170 mile trip with an 140mile detor along the way!