BEAM Projects > Modified EdgeBot

 

Keith's Modified Edgebot

My Modified Edgebot!

Grant's Edgebot Circuit

Edgebot Circuit by GrantM

Circuit used: Edgebot Circuit by GrantM; Be sure to check out his website! Loads of great info. Many thanks to Grant!

Behavior of Circuit: When a sensor is grounded, the motor on that sensor side stops. The other motor then reverses. The reverse time is based on the 22uf capacitor. This causes a back up and turn movement away from the tripped sensor.

Construction Notes: I am rebuilding this page from memory as it was lost and everything vanished. I am going to take the original schematic and modify it a bit. Instead of edge detectors, I am going to put in bump sensors to cause it to reverse on wheel at a time. Basically, the circuit will work exactly the same, but with different sensors. I have scratch-built the sensors from perfboard, 1/8th inch brass tubing, and some guitar wire.

October 7, 2008: Just a quick note. I reposted all of the photos, including the wheels which I finished just before my website problems started. The wheels will turn inside the tubes. I will have to afix a stop to keep the axle from pulling out once I assemble the chassis. I have pretty much decided that I will be using a battery holder for the main part of the body. I have also loosly wired up everything to test and it works fabulously! My next update will include pictures of the test setup.

October 9, 2008: I have a collection of general notes that I believe were included (not all but most) in the original page. Enjoy!

Sensor construction notes: Each sensor is a piece of 1/8th inch tubing, soldered to a piece of perf-board. A 3 inch piece of guitar wire is bent and soldered to the perf-board and the free end is extended through the brass tube. I plan on grounding the brass tube and connecting the wire to the 47K resistor attached to the AC14.

Testing notes
: If you look closely at the pulleys on the motors (1st test rig photo), you will see colored markings. These help me to see if they are turning. Also note on the back of the motors that one of the terminals has a dot next to it. I try to keep both motors wired the same, that way I can ensure that they are both rotating the same direction (unless you don't want them to...). Here I have the positive lead connected to the dot terminal. For testing, I just grounded the 47K resistor from the AC14 and the motor reversed for a bit. So, everything is working according to plan!

Other notes
: I need to add a switch to turn off battery power. Also, if I am going to use the batter holder as a structural part of the Edgebot, I will need to make sure the batteries can be removed easily.

October 14,2008: After trying different mounts for the axles and the existing pulley system and drive rubber bands, I found that the friction in the axles would not let the wheels to turn. One of the things I am going to try in the near future is a shorter fatter rubber band. I may have to totally rework the drive train...

October 27, 2008: I had to rework the axle/drive system because of friction and not enough torque from the motors. I actually came to two conclusions. First, 3V wasn't enough to really drive the system. Second, the wheels needed a tighter fit to the axle to reduce friction.

To answer the second question first: I went with a guide shaft from an old floppy drive as the axle. I drilled out the wheels to a hair larger than the new axle. The next question was how I was going to keep the wheel on the axle. I was going to just use hot melt glue, but it would not stick. So the solution was to cut two small notches at each end of the axle for the glue to hold on to. I also sanded each end, but it wasn't enough for the glue to hold on to (see pictures below). I will probably just use a piece of 1/8th inch brass tubing to keep it centered on the chassis.To answer the first question: I am going to run it off of a 9v battery and a 7805 to drop the voltage down to 5v.

More to come.

October 28, 2008: I re-thought out my end cap for the axle. It was dragging too much on the wheel. So, I made a thin plastic washer for both ends, put a dab of hot melt glue then flattened it out (see pictures below). I then measured between the wheels allowing for the 1/8th inch brass tube to fit just inside the pulleys. I brazed 3/4 of an inch piece of brass channel to the 1/8th inch tube. I then put the other plastic washer on the other end with a dab of hot melt glue. See all of the pictures below. I am going to use the brass channel to mount the axle to a piece of perf board that I am going to use for the body of the bot.

October 30, 2008: I got a bit more done. I had to rewire both motors. They were pushing instead of pulling. And I want this to be a tail dragger, not a tail pusher... I have everything mounted and am just about finished wiring up everything except the sensors. I wish I would have left a ground connection towards the front of the bot, it would have made things simpler. I ordered some 10mm blue LEDs a while ago (by mistake), so I am going to use one of them for the tail. I may even wire it up as a power on indicator. I think one more day of work and some fine tuning and it should be done!

October 31, 2008: She LIVES! Everything works as advertised including the light up LED tail skid! It isn't as pretty as Grant's... My bump sensors are not as responsive as I'd like, so I am going to do a little bit of fine tuning, perhaps change out the stiff wire for a finer brass wire. When one sensor is triggered, the tire on that side stops and the tire on the oppisite side reverses for a couple of seconds. Works great. I will get a few more for the BEAM Gallery after I fine tune it.

November 1, 2008: I reworked the sensors. I removed the stiff wire for a springy bit of brass wire. It was also alot easier to solder than the stiff wire. I made a cover for it out of a sheet of plastic purchased from my local hobby store. I relocated the on switch to the plastic cover. The cover is secured to the battery with some blue tack. Let me know what you think! Check out the BEAM Gallery for bigger pictures.

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Most of the parts
Most of the Parts


Edgebot engine - top view
Edgebot engine - top view

Edgebot Engine - remolded
Edgebot Engine - remolded

Sensor - upclose
Hand crafted sensors

 

Wheels, tubing, and cutter
Wheels, tubing, and cutter

 

Wheels and cut tubing
Wheels and cut tubing

 

Edgebot Test Rig
Edgebot Test Rig

 

Test Rig from oposite view
Test Rig from oposite view

 

New Wheels
New Wheels

New Axle

New Axle

 

Capped End
Capped End

Wheel Axle Assembly

Wheel Axle Assembly

 

Wheel End
Wheel End with plastic washer and hot melt glue

Wheel Axle Assembly

Wheel Axle - angle view 1

 

Right Side of Bot
Right Side of Bot, needs sensors hooked up

bottom of bot

Bottom of Bot

 

Rear of Bot
Rear of Bot - Needs Sensor hooked up

Top View of bot

Top View of Bot

 

Right Side of Bot
Right Side of Bot

 

Power and on switch

Power and on switch with 7805

 

Left Side of Bot
Left Side of Bot

 

Right Side

Right Side of Bot

 

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