CSE 480 Fall 2003 Group 1 Even more ESCs and H-Bridges We tested the current draw on our servo and main motor: Max current servo = 0.3A Max current motor.

CSE 480 Fall 2003 Group 1Even more ESCs and H-Bridges

• We tested the current draw on our servo and main motor:

• Max current servo = 0.3A

• Max current motor = 2A

Homemade Speed Controls

• http://www.math.niu.edu/~behr/RC/speed-ctl.html

• “Most home-grown ESC plans are by design simple. This also means that they will be, as a rule, less reliable and more temperamental than commercial units. An ESC is supposed to detect pulses whose width is varying a little bit, and convert those variations to a big voltage swing which controls the FET. All this has to happen in a nasty environment: vibration, interference from the motor, etc. It isn't a trivial job. “

• A few designs in the German Magazine, ElektroModell.

ESC using PIC Microcontroller ($??) http://homepages.paradise.net.nz/bhabbott/esc.html

Homemade H-Bridge (no break)• $1.60 1.5A, 8-DIP

http://www.robotroom.com/HBridge.htm l

Simple H-Bridge we built (3A)(untested)

PWM

5V

REF

1k

1k

1k

1k

MIN

Zetex ZHB6718 H-Bridge ($3.70)

Half-H/Full-H Drivers (~$2)

Cont.

Texas Instruments TPIC0107B ($4.28)

• 5A, 2kHz

• 20HSOP

Motorola 33886 ($6.22)

• 5.2A, 10kHz, 20HSOP

Heatsink Small OutlinePackage (HSOP)

• Our Prototype Board vs HSOP

MC33886 Development Board ($50)

Conclusions

• Anyone else find ESCs and H-Bridge designs?

• We could spend an entire semester just designing an ESC.

• This doesn’t even include the circuitry for the sensors.

• What level of abstraction should we use for sophomores? (Transistor level, IC level, ESC level)

Trying to find the right balance for the sophomore design project.

• CS portion is going to be decided on level of API abstraction.

• CE portion is probably under 25% since we’re not designing a CPU from scratch.

• Building a car from scratch could skew ME > 25%• Building an ESC from scratch could skew EE > 25%

The Optimal Balance

ME

EE

CE

CS