1. Power Sources & Management ECE 450

2. 2 Batteries Alkaline Power capacity: Medium* Weight: Heavy (30 Watt hours / Kg) Life cycle: One-time use Cost: Inexpensive Energy Output: Very Low Performance at low charge: Weak Self discharge rate: Low (< 2% of charge per year)* Cell Voltage:1.52V Lead Acid Power capacity: Low Weight: Heavy (30 Watt hours / Kg) Life cycle: ~800 charges Cost: Inexpensive Energy Output: Very Low Performance at low charge: Weak Self discharge rate: Low (<0.3% of charge per day) Cell Voltage:2V NiCad (Nickel Cadmium) Power capacity: Medium Weight: Medium (40 – 60 Watt hours / Kg) Life cycle: ~1500 charges (memory effect*) Cost: Inexpensive Energy Output: Medium Performance at low charge: Weak (tapers down gradually) Self discharge rate: Medium (1% of charge per day) * Cell Voltage:1.2V http://www.electrictoolguide.com/types-of-batteries

3. 3 Batteries NiMH (Nickel Metal Hydride) Power capacity: High Weight: Light (60 – 80 Watt hours / Kg) Life cycle: ~1000 charges Cost: Medium (some higher capacity models get expensive) Energy output: High – appropriate for high-demand applications Performance at low charge: Strong (dies suddenly) Self discharge rate: High (4% of charge per day)* Cell Voltage:1.2V Lithium (Li-ion) Power capacity: High – Very High Weight: Ultra-Light (100+ Watt hours / Kg) Life cycle: ~1200 charges Cost: High Energy Output: High Performance at low charge: Strong (usually gives a warning before dying) Self discharge rate: Low (<0.2% of charge per day) * Cell Voltage:3.6V Fuel Cell Power capacity: 2 to 3 times over Li-ion batteries Weight: Ultra-Light (100+ Watt hours / Kg) Life cycle: Refilled with methanol or ethanol Cost: High ($400) http://www.electrictoolguide.com/types-of-batteries

4. 4 Capacity Discharge vs Voltage http://www.societyofrobots.com/batteries.shtml (Alkaline)

5. 5 Temperature Effects Lithium Ion Batteries http://www.societyofrobots.com/batteries.shtml

6. 6 Storage Characteristics Lithium Ion Batteries http://www.societyofrobots.com/batteries.shtml

7. 7 Discharge Rates Lithium Ion Batteries http://www.societyofrobots.com/batteries.shtml

8. 8 Alkaline Batteries Not Fit for High Drain Electronic Devices

9. 9 Battery Connections GND VCC GND 1.5v 28mA Parallel Connection* Series Connection

10. Voltage Regulators

11. 11 MC7800, MC7800A, LM340, LM340A Series, NCV7805 APPLICATIONS INFORMATION Design Considerations The MC7800 Series of fixed voltage regulators are designed with Thermal Overload Protection that shuts down the circuit when subjected to an excessive power overload condition, Internal Short Circuit Protection that limits the maximum current the circuit will pass, and Output Transistor Safe– Area Compensation that reduces the output short circuit current as the voltage across the pass transistor is increased. In many low current applications, compensation capacitors are not required. However, it is recommended that the regulator input be bypassed with a capacitor if the regulator is connected to the power supply filter with long wire lengths, or if the output load capacitance is large. An input bypass capacitor should be selected to provide good high– frequency characteristics to insure stable operation under all load conditions. A 0.33  F or larger tantalum, mylar, or other capacitor having low internal impedance at high frequencies should be chosen. The bypass capacitor should be mounted with the shortest possible leads directly across the regulators input terminals. Normally good construction techniques should be used to minimize ground loops and lead resistance drops since the regulator has no external sense lead.

12. 12 Typical Bases TO-220TO-928-DIP8-SMD IC: Index Mark

13. 13 Schematic for a simple 7805-based power supply 7805 Unregulated input Ground Regulated Output To Robot Circuits +5 VDC C1 1  F C2 0.1  F + From 9V battery Or battery pack +7 VDC to +20 VDC

14. 14 Schematic for a simple 7805-based power supply 7805 Unregulated input Ground Regulated Output From 9V battery Or battery pack +7 VDC to +20 VDC To Robot Circuits +5 VDC C1 1  F C2 0.1  F + C3 100  F

15. Circuit Noise Bypassing is the reduction of high frequency current flow in a high impedance path by shunting that path with a bypass, usually a capacitor. Bypassing is used to reduce the noise current on power supply lines. Decoupling is the isolation of two circuits on a common line. The decoupling network is usually a low pass filter and the isolation is rarely equal in both directions. Decoupling is used to prevent transmission of noise from one circuit to another. In practice, bypassing is always used when decoupling. Most circuits require bypassing, not decoupling. Using decoupling techniques to accomplish bypassing will give disappointing, if not disastrous, results. Complete understanding of both concepts is vital. 15

16. 16 Schematic for a 7805-based power supply 7805 Unregulated input Ground Regulated Output From 9V battery Or battery pack +7 VDC to +20 VDC To Robot Circuits +5 VDC C1 1  F C2 0.1  F + C3 100  F C1 Bulk 220  F + C1 Bulk 220  F +

17. 17 Types of Capacitors TypeCapacitance Range Maximum Voltage AccuracyTemperature Stability LeakageComments Mica 1pF-0.01  F 100-600Good Excellent; good at RF Tubular ceramic0.5pF-100pF100-600SelectableSeveral tempcos (including zero) Ceramic 10pF-1  F 50-30,000Poor ModerateSmall, inexpensive, very popular Polyester (Mylar) 0.001  F-50  F 50-600GoodPoorGoodInexpensive, good, popular Polystyrene 10pF-2.7  F 100-600ExcellentGoodExcellentHigh quality; large; signal filters Polycarbonate 10pF-30  F 50-800Excellent GoodHigh Quality, small Polypropylene 100pF-50  F 100-800ExcellentGoodExcellentHigh quality; low dielectric absorption Teflon 1000pF-2  F 50-200ExcellentBest High quality, lowest dielectric absorption Porcelain 100pF-0.1  F 50-400Good Good long-term stability Glass10pF-1000pF100-600GoodExcellentLong-term stability Tantalum 0.1  F-500  F 6-100Poor High capacitance; polarized; small; low inductance Electrolytic 0.1  F-1.6F 3-600TerribleGhastlyAwfulPower-supply filters; polarized; short life Double layer0.1F-10F1.5-6Poor GoodMemory backup; high series resistance Oil 0.1  F-20  F 200-10,000GoodHigh-voltage filters; large; long life Vacuum1pF-5000pF2000-36,000ExcellentTransmitters

18. Capacitor Ratings 18

19. Capacitor Ratings 19

20. 20 Diodes Diode Schottky Diode Zener Diode

21. 21 Schematic for a 7805-based power supply Reverse Current Flow Protection 7805 Unregulated input Ground Regulated Output To Robot Circuits +5 VDC C1 1  F C2 0.1  F + D1 1N5817 (Schottky) From 9V battery Or battery pack +7 VDC to +20 VDC

22. 22 Schematic for a 7805-based power supply Overload of Regulated Voltage 7805 Unregulated input Ground Regulated Output To Robot Circuits +5 VDC C1 1  F C2 0.1  F + D1 1N5817 (Schottky) From 9V battery Or battery pack +7 VDC to +20 VDC ZD1 5.6V Zener 1N5232B

23. 23 Improvements to Simple 7805 Voltage Regulator 1.Include the capacitors suggested by the manufacturer. After that, add a bulk capacitor to the regulated output and to the unregulated power supply 2.Use a low-resistance, p-channel power MOSFET to prevent damage from a reverse battery 3.Add various low- and medium-value capacitors of different chemistries and technologies at various places on the circuit board to collectively benefit form their individual strengths. 4.Include at least one 0.1  F capacitor for every chip to bypass board impedance (providing a “local” power supply) and to decouple (isolate and reduce) circuit noise. Put each capacitor as close as possible to its targeted chip, and keep the lead length of each capacitor as short as possible. 5.Add a PPTC overcurrent-protection device to limit the maximum current that can flow through the robot. 6.Add a 5.6 V zener diode to the 5V regulated circuit to prevent damage from overload.

24. 24 Improved Schematic for a 7805-based power supply 7805 Unregulated input Ground Regulated Output battery pack To Robot Circuits +5 VDC C1 1  F C2 Bulk 220  F + D1 1N5817 (Schottky) C1 Bulk 220  F + + C2 0.1  F ZD1 5.6V Zener 1N5232B C4 1000  F + C4 0.1  F

25. 25 Butterworth Filters

26. 26