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Electronics for dummies - McComb G.

McComb G., Boes E. Electronics for dummies - Wiley publishing, 2005. - 433 p.
ISBN: 0-7645-7660-7
Download (direct link): electronicsfordummies2005.pdf
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2. Loosen the four casing screws from the bottom of the servo (see Figure 15-12).
3. Remove the screws completely so that you can set the servo base down on the table while youíre working inside it.
On a few servos, notably the GWS S03, you remove the case screws from the top, not the bottom.
4. Remove the top portion of the servo and observe how all the gears are oriented so you can put things back the same way when youíre done.
Look at Figure 15-13 for an example of what the innards of a servo look like.
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Chapter 15: Cool Robot Projects to Amaze Your Friends and Family 345
Figure 15-13:
A taken-apart servo. Note the placement for all the gears.
Remove the center gear, being careful not to unseat its metal shaft, and place the center gear aside.
On the Hitec HS-422, you canít easily remove the center gear without also lifting up the output gear, so carefully lift (and then replace) the output gear, if you need to.
Remove the output gear.
Use a small pair of pliers to set the potentiometer at its center position, as you can see in Figure 15-14.
Remove the ridge on the top side of the output gear by using the nippy cutters (see Figure 15-15), an X-ACTO blade, or a razor saw.
Exercise caution! The harder the plastic, the more likely it is that the ridge will break suddenly and fly off. Wear eye protection. Always nip first on the long side to prevent the output gear from breaking. When using an X-ACTO blade or razor saw, observe the obvious precautions against cutting your fingers off. If youíre using cutters, chip off small amounts of the ridge at a time, instead of trying to clip it off all at once Otherwise, the pressure of the cutter can cause the output gear to break apart.
5.
6.
7.
8.
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346 Part V: A Plethora of Projects
Figure 15-14:
Setting the potentiometer to its center position.
9. File down the small portion of the ridge that youíre stuck with, no matter what cutting technique you use; do this filing with a small, flat file (see Figure 15-16).
Figure 15-15:
Clipping off the ridge on the top of the output gear. Use caution!
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Chapter 15: Cool Robot Projects to Amaze Your Friends and Family 347
Figure 15-16:
Filing down the ridge.
10. Remove the metal retaining ring from the underside of the output gear (Figure 15-17), using the small-bladed screwdriver.
This ring holds the potentiometer shaft clip and supports the output gear.
11. Use the small-bladed screwdriver again to remove the potentiometer shaft clip, as shown in Figure 15-18.
12. Place the metal retaining ring back into the output gear.
13. Replace the output gear on its seat, resting over the potentiometer.
14. Replace the middle gear and make sure that all gears mesh properly.
15. Add more grease at this point, if necessary.
16. Finally, put the top case back on and screw in the four case screws.
Mounting the servos to the Rover
R/C servo motors have a screw flange that you can use to mount them permanently, but for the Smart Rover, just stick on some double-sided tape or Velcro to get the job done.
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348 Part V: A Plethora of Projects
Figure 15-17:
Taking out the retainer.
Figure 15-18:
Use a small screwdriver to remove the potentiometer shaft clip.
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Chapter 15: Cool Robot Projects to Amaze Your Friends and Family 349
We like to use a Velcro-like material called Dual Lock. 3M makes it, and you can find it at discount department stores, such as Target, and some hardware stores. Dual Lock works better at holding the parts of your robot together than Velcro because it doesnít permit as much side-to-side slippage.
Attach a piece of Dual Lock to the side of a servo. Stick a mating chunk of Dual Lock on the underside of Roverís bottom deck and squeeze the two pieces together to make a solid joint.
Figure 15-19 shows you what the servo looks like when youíve mounted it on the Rover.
When you attach the servos to your Rover, make sure that you get both servos on straight. Otherwise, the robot may wobble around the room like a toddler learning to walk. Be sure to leave enough clearance for the wheels; otherwise the wheels may scrape against the robot.
Figure 15-19:
Securing a servo to the bottom of Rover.
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350 Part V: A Plethora of Projects
Putting Your Servos on a Roll with Wheels
The motors on Rover have one reason for being ó to move the wheels and make the thing go. For the next step, after you attach the servo motors to the robot body (which we talk about in the preceding section), you have to attach wheels to the motors.
Several online and mail-order outfits, such as www.budgetrobotics.com and www.solarbotics.com, sell 2/2-inch diameter wheels that you can attach directly to an R/C servo motor. (You can make your own wheels, but servo-ready wheels donít cost much, and are easy to use, so why bother?) Find some wheels that you like, and be sure to buy two. When you buy wheels, select the correct type for the servo that youíre using. The mounting hub differs ever-so-slightly between Futaba and Hitec servos, so get two wheels of the same brand.
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