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BUREAU OF MINES 
 INFORMATION CIRCULAR/1989 
 
 Intrinsically Safe 5-V, 4-A 
 Rechargeable Power 
 Supply 
 
 By John J. Sammarco 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
Mission: As the Nation's principal conservation 
 agency, the Department of the Interior has respon- 
 sibility for most of our nationally-owned public 
 lands and natural and cultural resources. This 
 includes fostering wise use of our land and water 
 resources, protecting our fish and wildlife, pre- 
 serving the environmental and cultural values of 
 our national parks and historical places, and pro- 
 viding for the enjoyment of life through outdoor 
 recreation. The Department assesses our energy 
 and mineral resources and works to assure that 
 their development is in the best interests of all 
 our people. The Department also promotes the 
 goals of the Take Pride in America campaign by 
 encouraging stewardship and citizen responsibil- 
 ity forthe public lands and promoting citizen par- 
 ticipation in their care. The Department also has 
 a major responsibility for American Indian reser- 
 vation communities and for people who live in 
 Island Territories under U.S. Administration. 
 
C '^^ '- / 
 
 Information Circular 9223 / z' - - 
 
 i 
 
 Intrinsically Safe 5-V, 4-A 
 Rechargeable Power 
 Supply 
 
 By John J. Sammarco 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 Manuel Lujan, Jr., Secretary 
 
 BUREAU OF MINES 
 T S Ary, Director 
 
no.qaa3. 
 
 Library of Congress Cataloging in Publication Data: 
 
 Sammarco, John J. 
 
 Intrinsically safe 5-V, 4-A rechargeable power supply. 
 
 (Bureau of Mines information circular; 9223) 
 
 Includes bibliographical references. 
 
 Supt. of Docs, no.: I 28.27:9223. 
 
 1. Electricity in mining-Safety Measures. 2. Storage batteries. I. Title. 
 II. Series; Information circular (United States. Bureau of Mines); 9223. 
 
 ^TN295.U4 [TN343] 622 s [622'.8] 88-607917 
 
CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 2 
 
 Acknowledgment 3 
 
 Circuit description 3 
 
 Main regulator circuit 3 
 
 Input protection circuit 4 
 
 Output protection circuit 5 
 
 Circuit calibration 6 
 
 Local regulation network 7 
 
 Specifications 7 
 
 Summciry 8 
 
 Appendix A.-Intrinsic safety 9 
 
 Appendix B. -Fabrication information 10 
 
 Appendix C.-Battery charger 11 
 
 ILLUSTRATIONS 
 
 1. 5-V dc power supply 2 
 
 2. 5-V dc power supply block diagram 3 
 
 3. 5-V dc power supply schematic diagram 4 
 
 4. Main regulator circuit 4 
 
 5. Input protection circuit 5 
 
 6. Output protection circuit 6 
 
 7. Local regulation network 7 
 
 C-1. Battery charging circuit schematic 11 
 
 TABLE 
 
 1. Resistor adjustments 6 
 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 
 
 A 
 
 ampere 
 
 /zF 
 
 microfarad 
 
 "C 
 
 degree Celsius 
 
 mA 
 
 milUampere 
 
 h 
 
 hour 
 
 s 
 
 second 
 
 in 
 
 inch 
 
 V 
 
 volt 
 
 lb 
 
 pound 
 
 Vdc 
 
 volt, direct current 
 
 kohm 
 
 kilohm 
 
 W 
 
 watt 
 
INTRINSICALLY SAFE 5-V, 4-A RECHARGEABLE POWER SUPPLY 
 
 By John J. Sammarco^ 
 
 ABSTRACT 
 
 The U.S. Bureau of Mines has developed a regulated, intrinsically safe, rechargeable power supply 
 for portable electronic equipment for underground use. The regulated output is ideal for microprocessor 
 power requirements and is suited for operation in hazardous environments. Two rechargeable, sealed 
 batteries are contained within the power supply. Provisions are made to use an external source of power 
 if these batteries fail. Provisions are also made to charge these internal batteries when needed. The 
 circuit is composed of three main circuits: the main regulator circuit, the input protection circuit, and 
 the output protection circuit. The main regulator circuit provides remote voltage sensing, current 
 sensing, fault monitoring, and internal thermal protection. The input protection circuit checks for 
 excessive input current and low battery conditions. The output protection circuit contains two 
 overvoltage detection devices. 
 
 Schematics, a parts list, and a calibration procedure are provided in this report to enable readers to 
 fabricate the power supply. 
 
 ^Electrical engineer, Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA. 
 
INTRODUCTION 
 
 NOTE -With the internal battery, the assembly is regarded as intrinsically safe. If the external 
 source is used, the assembly and its associated equipment must remain in a nonhazardous area 
 (fresh air). Battery charging must always be done in fresh air. Any alteration of the device as 
 described in this report voids intrinsically safe operation and its subsequent approval. 
 
 Bureau research results provide advancements in safety 
 and increases in overall mining efficiency through im- 
 proved technology. This research may result in devices 
 that can readily be used by the mining industry, such as the 
 intrinsically safe, rechargeable power supply (fig. 1) de- 
 scribed in this report. 
 
 The power supply was designed for portable, electronic 
 equipment used in hazardous environments. For this 
 application, the following criteria are noteworthy: The 
 design must be intrinsically safe (see appendix A); circuit 
 operation should be efficient to maximize battery life; and 
 size and weight should be minimal to enhance portability. 
 
 To meet these criteria, the design incorporates multiple 
 and redundant protection circuits to ensure intrinsic safety. 
 Integrated circuits incorporating multiple protection func- 
 tions were used to minimize circuit count, thus reducing 
 the size and increasing reliability. Components were se- 
 lected to enable efficient operation to prolong battery life. 
 A means for recharging the batteries exists. 
 
 This report describes circuit operation, calibration, and 
 gives parts lists and schematic diagrams for both the power 
 supply and a battery charger. 
 
 Figure 1.-5-V dc power supply (closed and open). 
 
ACKNOWLEDGMENT 
 
 The author wishes to acknowledge John S. Gbruoski, 
 electronics technician, Pittsburgh Research Center, for 
 construction of the device and for assistamce during the 
 
 testing and Mine Safety 
 (MSHA) approval process. 
 
 and Health Administration 
 
 CIRCUIT DESCRIPTION 
 
 A block diagram of the power supply is depicted in 
 figure 2. The power supply circuit schematic is depicted in 
 figure 3. This power supply circuit is composed of the 
 main regulator circuit, the input protection circuit, and the 
 output protection circuit. A description of operation for 
 each of these circuits follows. 
 
 MAIN REGULATOR CIRCUIT 
 
 The functions of the main regulator circuit, shown in 
 figure 4, are to convert the 8-V nominal battery voltage to 
 a 5.0-V output, to provide protection from excessive cur- 
 rent, and to provide protection from voltage fault condi- 
 tions. The main regulator circuit achieves these functions 
 with device Ul, a programmable linear voltage regulator. 
 This part was selected because it contains provisions for 
 remote voltage sensing, current sensing, fault monitoring, 
 and internal thermal protection. Additionally, these 
 
 features, incorporated on one chip, greatly reduce the need 
 for external circuitry and simphfies design.'' 
 
 Linear voltage regulation is achieved by Ul (pin 9) 
 monitoring the output voltage at the remote sensing volt- 
 age divider resistors (R6 and R7). The appropriate biasing 
 is supplied to the series pass transistor Ql to maintain 
 proper output voltage regulation. An increase in output 
 voltage measured by Ul (pin 9) will cause the biasing of 
 Ql to decrease. Ql becomes less conductive and the out- 
 put voltage will decrease to the desired level of output 
 voltage. Various output voltages can be obtained by sim- 
 ply chcmging the remote sensing voltage. Potentiometer 
 R7 enables changes in the remote sensing voltage divider 
 network so that the output voltage can be adjusted. Once 
 
 ^Fritz, G. Versatile UC1834 Optimizes Linear Regulator Efficiency. 
 Unitrode Corp., Application Note U-95, 1984, pp. 1-12. 
 
 8-V dc 
 battery 
 source 
 
 Switch 1 
 
 ON 
 
 EXT. 9 
 
 Input 
 
 protection 
 
 network 
 
 8 V dc 
 
 d> 
 
 Main 
 regulator 
 
 circuit 
 
 5Vdc 
 
 ^ 
 
 Output 
 
 protection 
 
 circuit 
 
 External 
 connector 
 
 External * 
 power 
 source 
 (User supplied) 
 
 V 
 
 Output, 
 5-Vdc, 4A 
 
 Switch 1 must be in the EXT. position to 
 use battery charger or external power 
 
 Figure 2.-5-V dc power supply block diagram. 
 
J2-2 
 
 To battery 
 
 sense CR1 CR2 CR3 
 
 KEY 
 
 rFI Indicates cofinections made to printed 
 
 circuit board in tteat sink areo 
 
 Heat sink, o\ Dl D2, D3 
 
 +5Vdc + Vo 
 
 Figure 3.-5-V dc power supply schematic diagram. 
 
 ®TP5 ®TP6 
 
 />^ 
 
 Figure 4.-Main regulator circuit 
 
 the voltage has been adjusted in a laboratory environment, 
 no changes to this adjustment should be made while 
 underground. 
 
 Current sensing is used to limit the current into Ql to 
 protect it from daunage cmd to regulate the maximum out- 
 put current of the power supply. The input current is 
 sensed by measuring the voltage across R25 vwth a current 
 sensing amplifier internal to Ul. When current becomes 
 excessive the base drive to Ql is decreased making Ql less 
 conductive, which limits the output current. 
 
 Output voltage fault detection provides protection for 
 two separate voltage fault conditions-overvoltage and 
 undervoltage of the output. The voltage fault detection 
 will tolerate any voltage deviation within ±10% of the 
 nominal output voltage. Any voltage outside this range 
 will be treated as a fault. An overvoltage fault activates a 
 crowbar circuit that switches on a shunt silicon-controlled 
 rectifier (SCR). This effectively places a short circuit 
 across the output causing a large increase in Ql's collector 
 current. Before this current becomes excessive, the cur- 
 rent sensing protection of Ul will activate to provide 
 proper protection. 
 
 A voltage fault delay line prevents transient voltage 
 conditions from triggering the overvoltage and undervolt- 
 age fault protection circuits. This delay is programmable 
 by adding a capacitor from pin 11 to ground. The delay 
 time is about 0.047 s for each microfarad of capacitance. 
 
 Finally, a thermal shutdown circuit is incorporated in 
 Ul. This circuit will shut down operation of Ul when the 
 internal junction temperatures reach 165° C. This protects 
 Ul from damage because of excessive power dissipation. 
 
 INPUT PROTECTION CIRCUIT 
 
 The input protection circuit of figure 5 serves two main 
 functions: to provide protection against excessive input 
 current and to detect low battery conditions. 
 
 Excessive input current protection is needed to protect 
 the main regulation circuit from damage because of over- 
 heating and to limit the output current of the power supply 
 to a safe level. The input current is limited to approxi- 
 mately 4.0 A. This is achieved by sensing the current 
 through R2 and turning Q2 off when excessive current is 
 
(To battery sense) 
 -J2-2 
 
 CRl CR2 CR3 
 — <] — <1 — W— »To external power 
 
 F1 
 
 and battery 
 charger 
 
 TP3® 
 
 5^l kn 
 
 -^/4' 
 
 02 ^ 
 Figure 5.-lnput protection circuit. 
 
 detected, thus opening the negative connection to the 
 battery. The input current (I) is known by simply measur- 
 ing the voltage across R2 (E) and applying Ohm's law 
 where E = I * R. 
 
 A voltage of 0.2 V will exist across the 0.05-ohm resis- 
 tance of R2 when 4.0 A of input current is present. This 
 0.2 V is amplified to about 6.64 V by the differential am- 
 plifier circmt of U2. Next, this voltage is sent to the volt- 
 age detection circuit of U3. When a 6.64-V or greater 
 voltage is detected by U3, the gate of Q2 is biased to turn 
 off Q2, thus disconnecting power from the battery to the 
 power supply circuit. 
 
 The circuit described for current protection is indepen- 
 dent and redundant to the current protection circuitry of 
 Ul described in the "Main Regulator Circuit" section. 
 Overcurrent protection is also provided by fuse Fl. How- 
 ever, a fuse is not recognized as a protection device when 
 evaluating a circuit for intrinsic safety because the re- 
 sponse time of the fuse is not adequate to prevent an igni- 
 tion in a hazardous environment. 
 
 The second function of the input protection circuit is to 
 detect low battery conditions. Operation of the power 
 supply during low battery voltages can deep discharge the 
 batteries, which will shorten their useful hfe. Two 3.95- V, 
 rechargeable, sealed batteries connected in series are used 
 as the power source. This combination gives a total nom- 
 inal working voltage of 7.9 V. When a low battery condi- 
 tion of 6.5 V is detected by the circuitry of U3, the metad- 
 lic oxide semiconductor field-effect transistor Q2 is turned 
 off to disconnect the negative side of the batteries from the 
 power supply circuitry. When the battery voltage increases 
 to 6.6 V, U3 will turn Q2 on, thus restoring battery power 
 to the power supply circuit. 
 
 Device U3 is used in the overcurrent detection circuit 
 and the low-battery-detection circuit. This is a dual volt- 
 age detector device that operates from any supply voltage 
 in the 1.6- to 16-V range and can monitor voltages greater 
 than 1.3 V. The voltage detection trip points and hystere- 
 sis levels are programmed by external resistor networks.^ 
 U3 is a low-power complementary metallic oxide semicon- 
 ductor (CMOS) device and typically requires only 3 mA 
 for operation, thus minimizing the current drain on the 
 batteries. 
 
 Note that the input circuit also provides the ability to 
 externally sense battery voltage, supply external power, and 
 charge batteries. An external Une is designated for sensing 
 battery voltage. This provides easy access for measure- 
 ment of the battery voltage. A separate line is provided 
 for external power operation or for battery charging. 
 When power switch SWl is opened (off), the batteries can 
 be bypassed so that external power can be supplied for 
 operation. 
 
 The maximum external voltage permitted through this 
 line is 16 V. To charge the batteries, SWl must be closed 
 and the battery charger must be connected. Information 
 for the battery chcu^ger is given in appendix C. The bat- 
 teries recharge at a constant potential source of 4.96 to 
 5.10 V dc each, with a charging current of 1.2 A. 
 
 CAUTION.-Do not attempt to recharge, replace, or 
 connect batteries while in a hazardous environment. 
 Also, do not attempt to use or connect external 
 power while in a hazardous environment. 
 
 OUTPUT PROTECTION CIRCUIT 
 
 A separate and redundant overvoltage protection circuit 
 is present at the output as shown in figure 6. Shunt SCR 
 circuits will be activated when an overvoltage condition 
 exists. Two identical shunts are provided. This redundan- 
 cy provides protection if a failure would occur in one of 
 the shunts. The level at which the SCR's will turn on is 
 determined by resistive divider networks. These trip levels 
 can be adjusted. Potentiometer R9 adjusts the level for 
 SCR D2 and potentiometer Rll adjusts the level for SCR 
 D3. 
 
 When a shunt SCR turns on, it effectively makes a 
 short-circuit connection across the output of the power 
 supply. During short-circuit output conditions, a large 
 short-circuit current will flow through the power supply. 
 The power supply will shut down when this current ex- 
 ceeds the levels set by the current protection devices. 
 Once £m SCR has tripped, it must be reset by momentarily 
 disconnecting battery supply voltage by toggling power 
 supply switch SWl to the off position. 
 
 ^Maxim Integrated Products Inc. (Sunnyvale, CA). Maxim Power 
 Supply Circuits Data Book. 1986, pp. 113-123. 
 
(«)TP1 
 
 + 5 Vdc ^ w 
 
 OUT 
 
 B'^ ^ 
 
 'OUT 
 
 ®TP2 
 Figure 6.-0utput protection circuit. 
 
 CIRCUIT CALIBRATION 
 
 Once circuit construction is completed, it is necessary 
 to adjust and calibrate the circuit to insure proper opera- 
 tion. All adjustments, after setting, should remain fixed. 
 No adjustments should be made whUe undergroimd. First 
 the nominal output voltage is adjusted, then the output 
 overvoltage protection trip points are set. 
 
 Before the nominal output voltage can be set, it is nec- 
 essary to temporairily prevent the overvoltage protection 
 circuits of D2 and D3 from tripping. If these trip points 
 are below the nominal output voltage, D2 and/or D3 will 
 turn on and prevent the adjustment of the output voltage. 
 To set the trip points above nominal, adjust R9 and Rll 
 fully clockwise. Next, with battery voltage appUed to the 
 circuit, connect a load resistance of 2 ohms (15-W mini- 
 mum) to the output and adjust R7 until 5 V dc is mea- 
 sured from test points TPl to TP2. 
 
 To set the output overvoltage protection trip points, 
 disconnect the batteries from the circuit and remove Ul 
 and the 2-ohm output load. Connect a variable power 
 supply capable of providing at least 6 V at 1 A to the out- 
 put of the power supply circuit. This connection should 
 include a 2-ohm, 15-W current limiting resistor in series 
 
 from the positive terminal of the variable power supply to 
 the positive output terminal of the intrinsically safe power 
 supply. Set the voltage of the variable power supply to 5.3 
 V dc. Turn R9 counterclockwise until SCR D2 turns on 
 and draws significant current from the variable power sup- 
 ply. Next, increase the voltage to 5.35 V dc and then turn 
 off the variable power supply to reset D2. Turn the power 
 supply on and adjust Rll until D3 turns on. Turn off the 
 variable power supply and disconnect it from the output. 
 Replace Ul. This completes the calibration. Table 1 lists 
 the resistors used in the calibration sequences and their 
 adjustment ranges. 
 
 Table 1. -Resistor adjustments 
 
 Potentiometer Adjustment Range, V dc 
 
 R7 Allows output voltage to be 3.2- 5.5 
 
 adjusted. 
 
 R9 Varies trip point of rectifier D2 3.2-12.0 
 
 for overvoltage protection. 
 
 Rll Varies trip point of rectifier D3 3.2-12.0 
 
 for overvoltage protection. 
 
LOCAL REGULATION NETWORK 
 
 Although the output of the power supply is limited to a 
 nominal output of 5 V, it can be used in a variety of appli- 
 cations requiring multiple voltages by using a local regula- 
 tion network (note that any additional circuits connected 
 to the power supply must also be evaluated for intrinsic 
 safety). For example, figure 7 depicts a system requiring 
 multiple voltages. By using the 5-V supply as the primary 
 voltage, the other voltages can be derived at each circuit 
 board as needed. For instance, ±15 V can be derived 
 from 5 V using a voltage converter such as the Maxim 
 max680.'' This is a low-power, CMOS, dc-to-dc converter 
 that comes in an 8-pin, dual in-line package. This chip 
 requires only four external capacitors to complete the 
 circuit design and can operate up to 95% in voltage 
 conversion efficiency. 
 
 This approach increases flexibiUty because the 5-V sup- 
 ply can be used in various appUcations without redesign. 
 Other desired voltages can be derived as needed. 
 
 ''Reference to specific products does not imply endorsement by the 
 U.S. Bureau of Mines. 
 
 5-V do 
 
 intrinsically safe 
 
 power source 
 
 5-V 
 
 Board 1 
 
 Local 
 ± 15-V 
 regulator 
 
 Board 2 
 
 Local 
 ± 12-V 
 regulator 
 
 Board 3 
 
 'egulotor 
 
 Figure /.-Local regulation network. 
 
 SPECIFICATIONS 
 
 NOTE.-AIl speciflcations pertain to circuit operation at room temperature. 
 
 Min 
 
 Max Nominal 
 
 5.5 
 NAp 
 
 8.5 
 16.0 
 
 Typical 
 
 0.8 
 
 2.7 
 
 63 
 1.5 
 
 22 
 5.5 
 
 4.0 
 
 4.0 
 
 1.25 
 
 5.0 
 3.3 
 
 7.9 
 7.9 
 
 Output: 
 
 Adjustable voltage (Vj^, 7.9 V dc; load, 1.5 ohms; output voltage values as obtained 
 by varying potentiometer R7) V dc . . 3.2 
 
 Current (V^^, 7.9 V dc; V„„„ 5.0 V dc) : A . . NAp 
 
 Input voltage, V dc: 
 
 From battery pack 6.8 
 
 From external voltage source 6.8 
 
 Regulation, %: 
 
 Line (V^^, 6.8 to 8.4 V dc; load, 1.5 ohms) 
 
 Load (load current, 0.7 to 2.8 A; V^, 7.9) 
 
 Miscellaneous: 
 
 Efficiency (V^, 7.9; V„„„ 5.0; load, 1.5 ohms) % . . 
 
 Battery hfe (V„^„ 5.5; load, 1.5 ohms; initial V^^, 8.44; final V^, 7.04) h . . 
 
 Maximum power output W . . 
 
 Weight (includes battery weight) lb . . 
 
 Dimensions, in: 
 
 Width 
 
 Height 
 
 Length 
 
 NAp Not applicable. 
 
SUMMARY 
 
 An intrinsically safe power supply with a regulated out- The power supply incorporates detection and protection 
 
 put of 5 V at 4 A has been developed by the U.S. Bureau against excessive voltage and current, excessive circuit 
 
 of Mines. Two rechargeable, sealed batteries are used as junction temperatures, and low battery conditions, 
 
 the internal power source. External connections are pro- Complete information is supplied on circuit operation 
 
 vided to monitor battery voltage, recharge the batteries, and calibration so that this power supply can easily be 
 
 and to operate with an external power source connection. duplicated for industry use. 
 
APPENDIX A.-INTRINSIC SAFETY 
 
 The Code of Federal Regulations^ defines intrinsic 
 safety as "incapable of releasing enough electrical or 
 thermal energy under normal or abnormal conditions to 
 
 ^U.S. Code of Federal Regulations. Title 30-Mineral Resources; 
 Chapter I-Mine Safety and Health Administration, Department of 
 Labor; Subchapter B-Testing, Evaluation, and Approval of Mining 
 Products; Part 18-Electric Motor-Driven Mine Equipment and 
 Accessories; Subpart A-General Provisions, Section 18.2, July 1, 1987. 
 
 cause ignition of a flammable mixture of methane or 
 natural gas and air of the most easily ignitable 
 composition." 
 
 The power supply has been tested by the Mine Safety 
 and Health Administration (MSHA). Experimental Permit 
 No. 596 has been issued to the Bureau for this device as it 
 is used to power a specific system. Others wishing to use 
 this power supply must have it certified by MSHA for use 
 in their specific system. 
 
10 
 
 APPENDIX B.-FABRICATION INFORMATION 
 
 This appendix contains a list of parts needed to construct the rechargeable, intrinsically safe power supply described 
 in this report. 
 
 Item 
 
 Battery: Bl, B2 
 
 Capacitor: 
 
 C2 
 
 C3 
 
 C4, C5, C6 
 
 C7 
 
 C8, C9 
 
 CIO 
 
 Diode: CRl, CR2, CR3 . . 
 
 Fuse: Fl 
 
 Linear regulator: 
 
 Ul 
 
 U2 
 
 U3 
 
 Rectifier: 
 
 Dl, D2, D3 
 
 D4 
 
 Resistor: 
 
 Rl 
 
 R2 
 
 R3 
 
 R4 
 
 R5 
 
 R6 
 
 R7 
 
 R8, RIO, R12 
 
 R9, Rll 
 
 R13, R15 
 
 R14, R16, R18 
 
 R17 
 
 R19 
 
 R20 
 
 R21 
 
 R22 
 
 R23 
 
 R24 
 
 R25 
 
 R26 
 
 Switch: SWl 
 
 Transistor: 
 
 Ql 
 
 Q2 
 
 SCR Silicon-controlled rectifier, 
 WW Wire wound. 
 
 Description 
 CMF4V10 
 
 OMl-nF, 50-V dc, monolithic . . . 
 
 0.47-/iF, 35-V dc, tantalum 
 
 l-/iF, 35-V dc, tantalum 
 
 6.8-^F, 15-V dc, tantalum 
 
 0.22-^F, 50-V dc, tantalum 
 
 0.1-/iF, 50-V dc, monohthic .... 
 
 1N5823A 
 
 4-A, 250- V, type ABC, ceramic . 
 
 UC3834N 16-pin IC 
 
 LM308N 8-pin IC 
 
 ICL7665CPA 8-pin I 
 
 2N6400 SCR's TO-220 (case) . . . 
 SA6.0A TransZorb 
 
 10-ohm, WW, 10-W 
 
 0.05-ohm, WW, fused, 2-W 
 
 680-ohni, 1%, metal film 
 
 15-ohm, 5%, WW, 1/2-W 
 
 l-kohm, 1%, metal film 
 
 1.2-kohm, 1%, metad film 
 
 l-kohm (25T) #3299W ... 
 
 8.25-kohm, 1%, metal film 
 
 20-kohm (25T) #3299W 
 
 10-kohm, 5% 
 
 210-kohm, 1%, metal fihn 
 
 132-kohm, 1%, meted film 
 
 47.5-kohm, 1%, metal film 
 
 52.1-kohin, 1%, metal film 
 
 210-kohm, 1%, metal film 
 
 3.92-kohm, 1%, metal film 
 
 10-kohm, 5%, 1/4-W 
 
 150-ohm, 5%, 1-W 
 
 0.04-ohm, WW, 3-W, LPW3-2L . 
 
 1.8-kohm, 5%, 1/2-W 
 
 MTM-106D-RA PC-switch SPDT 
 
 D45VH1 
 
 IRF153 
 
 Manufacturer 
 
 Quantity 
 
 Eagle Pitcher 
 
 MaUory . . . . 
 
 . . do 
 
 . . do 
 
 . . do 
 
 . . do 
 
 . . do 
 
 Mot 
 
 Little Fuse . 
 
 Unitrode 
 
 National Semiconductor 
 Maxim 
 
 Mot 
 
 General Semiconductor 
 
 Dale 
 
 IRC 
 
 Dale 
 
 IRC-TRW 
 
 Dale 
 
 . . do 
 
 Bourns 
 
 . . do 
 
 . . do 
 
 IRC 
 
 Dale 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 IRC 
 
 IRC 
 
 IRC 
 
 IRC 
 
 Alco 
 
 GE 
 GE 
 
 1 
 1 
 3 
 1 
 2 
 1 
 3 
 1 
 
 1 
 1 
 1 
 
 3 
 1 
 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 3 
 2 
 2 
 3 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 1 
 
 1 
 
 1 
 
11 
 
 APPENDIX C.-BATTERY CHARGER 
 
 The information presented in this appendix is sufficient for construction of the battery charger designed for the Bureau 
 of Mines. This charger is not intrinsically safe. Do not attempt to use it in hazardous environments. Battery charging 
 and replacement must be conducted in a safe, fresh air environment. The parts Ust and schematic diagram (fig. C-1) 
 follow. 
 
 Item 
 
 Capacitor: 
 
 Cll 
 
 C12 
 
 C13 
 
 Diode: 
 
 CR12 
 
 CR13 
 
 Diode bridge: Dl . . 
 Linear regulator: U9 
 Resistor: R9, RIO . . 
 Transformer: Tl . . . 
 
 Description 
 
 Manufacturer 
 
 Quantity 
 
 2,100-/xF, 35-V dc 
 
 0.1-/iF, 50-V dc 
 
 l-/iF, 35-V dc 
 
 31DQ03 IR 
 
 80SQ035 IR 
 
 Type KBPC602 
 
 UA78GUIC 
 
 RN65C, 39.2-kohm, 1% 
 Type P-8642 
 
 Mallory 
 
 . . do 
 
 . . do 
 
 International Rectifier 
 
 . . do 
 
 General Instrument . . 
 
 Fairchild 
 
 Dale 
 
 Stancor 
 
 Current 
 transformer, 
 12.6 V, 6A 
 
 CRI3 
 
 + Cll 
 
 =^2,IOOyU.F 
 
 35 V 
 
 80S0035 
 IR 
 
 CI2 
 
 0.1 ziF: 
 
 50 V 
 
 U9 
 
 UA78GUIC 
 Ground Sense 
 
 q::CI3 
 1/iF 
 35 V 
 
 R9 
 
 • — 'vw- " — ^A/v 
 
 39.2 kn 
 17. 
 
 CRI2 
 
 -^ 
 
 3ID003 
 IR 
 
 RIO 
 
 39.2 kO 
 l.7o 
 
 J 2-4 
 
 — > 
 
 J2-2 
 
 J2-3 
 
 Chassis box, mechanical ground 
 
 1 
 
 D-^ 
 
 Safety 
 ground 
 
 Figure C-1 .-Battery charging circuit schematic. 
 
 us. GOVERNMENT PRINTING OFFICE: 611-012/00.085 
 
 INT.BU.OF MINES,PGH.,PA 28923 
 
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