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Build this multi-purpose Fast Battery Charger For tools, camcorders, R/C equipment & car batteries Last month, we presented the circuit and operating de­tails for this charger. This month, we conclude with the con­struction details and parts list. Pt.2: By JOHN CLARKE The Multi-Purpose Fast Battery Charger is housed in a plas­tic instru­ ment case measuring 257 x 190 x 85mm. All the circuitry is mounted on one PC board coded 14302981 and measuring 121 x 173mm. Two versions of the TEA1102 battery management IC are being made, a 20-pin dual inline package (DIP) and a 20-pin surface mount package. We have made pro­ vision for the surface mount version of the TEA1102 by means of a small 46  Silicon Chip carrier PC board coded 14302982 and measuring 29 x 16mm. We’ll talk more about this aspect later on. The power transformer (T1) is mounted sideways on the rear metal panel of the case, as shown in the photographs. Note that the inte­ gral ribs and bushes within the case will need to be removed in the area where the transformer mounts. The ribs can be removed with a sharp chisel while the bushes are eas­ ily cut out with a large, sharp drill bit. The main PC board is secured with self-tapping screws into the four bush­ es under the corner mounting holes in the PC board. Remove the other integral bushes under the board with a large drill. The component layout for the main PC board is shown in Fig.1. Before you install any parts on the PC board, it is wise to check it against the pattern of Fig.5. There should not be any shorts or breaks between tracks or any undrilled holes. Fix any defects before proceeding. Then you can begin by installing the PC stakes at the various external wiring connection points on the PC board. Next, install the wire links and resistors and then the diodes and zener diodes. Take care with their orienta­ tion and be sure to put each type in its correct place. As already noted, the TEA1102 (IC1) Fig.1: this component layout shows IC1 as a conventional dual in-line package but it may be supplied as a surface mount package. In that case, you will need to use the carrier PC board at right. may be supplied as a conventional dual in-line package (DIP) which can be soldered directly into the PC board or it may be a surface mount type. If you have the surface-mount type, you will need to mount it on the carrier board. This is coded 14302982 and measures just 29 x 16mm. It is assem­ bled as follows. First, check the pattern for shorts between the tracks and then pre-tin the copper lands where the IC pins will be placed. This done, insert and solder the two 10-way pin headers into the PC board so that the plastic holders are on the opposite side to the copper pattern. Next, place the surface-mount IC in position and, using a fine-tipped soldering iron, apply heat to each pin so that it melts the solder on the PC land. Check that each pin is soldered by measuring between the pin header connection and the IC pin with a mul­ timeter set to read Ohms. Check also that there are no shorts between pins. When the carrier board is complete, March 1998  47 Resistor Colour Codes ❏ No. ❏  1 ❏  3 ❏  1 ❏  3 ❏  1 ❏  1 ❏  4 ❏  2 ❏  2 ❏  1 ❏  1 ❏  1 ❏  2 ❏  1 ❏  1 ❏  4 ❏  2 ❏  1 ❏  1 ❏  1 ❏  1 Value 330kΩ 220kΩ 150kΩ 100kΩ 82kΩ 68kΩ 33kΩ 27kΩ 22kΩ 18kΩ 15kΩ 12kΩ 10kΩ 4.7kΩ 3.3kΩ 2.2kΩ 1kΩ 680Ω 470Ω 68Ω 10Ω Fig.2: the main switching inductor is bifilar wound, with two strands of 1mm enamelled copper wire. it can be inserted into the main PC board and soldered in position. Make sure that the IC is oriented correct­ ly. The remaining ICs can now be installed, taking care to orient them correctly, as shown in Fig.1. The two power transistors and two power diodes are mounted with their metal flanges towards the edge of the 48  Silicon Chip 4-Band Code (1%) orange orange yellow brown red red yellow brown brown green yellow brown brown black yellow brown grey red orange brown blue grey orange brown orange orange orange brown red violet orange brown red red orange brown brown grey orange brown brown green orange brown brown red orange brown brown black orange brown yellow violet red brown orange orange red brown red red red brown brown black red brown blue grey brown brown yellow violet brown brown blue grey black brown brown black black brown PC board. Do not cut their leads short because you will have to bend them to enable the flanges to be mounted on the rear panel for heatsinking; we’ll come to that later. You can install the capacitors next. The electrolytic ca­pacitors must be oriented with the correct polarity ex­ cept for the 3.3µF bipolar type which can go in either way. The five LEDs are installed so that they stand with about 12mm of lead length above the board. Later they will be bent over to protrude through the bezels in the front panel. Be sure that they are oriented correctly. Winding L1 L1, the main switching inductor, is wound on a plastic transformer bobbin which is then soldered into the main board. Fig.2 shows how it is wound. Two lengths of 1mm enamelled copper wire are bifilar wound from one side of the bobbin to the other. You need to strip the enamel from the ends of two lengths of 1mm wire and then solder them to pins on the one side of the transformer bobbin. The actual pins used on each side of 5-Band Code (1%) orange orange black orange brown red red black orange brown brown green black orange brown brown black black orange brown grey red black red brown blue grey black red brown orange orange black red brown red violet black red brown red red black red brown brown grey black red brown brown green black red brown brown red black red brown brown black black red brown yellow violet black brown brown orange orange black brown brown red red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown blue grey black gold brown brown black black gold brown Capacitor Codes ❏ Value IEC ❏ 0.1µF 100n ❏ 0.0018µF 1.8n ❏ 820pF 820p EIA 104 182 821 the bobbin are not important since the pins on each side are connect­ed together by the PC pattern. Now bifilar wind on 10 turns (ie, both lengths of wire at the same time), with each turn placed neatly on the bobbin Once wound, terminate the wires onto the pins on the opposite side of the for­ mer. Again, the actual pins used are not important and you will need to ensure that the enamel is stripped off the wire ends before soldering. Insert one of the core halves in place and secure it with a clip. Now place the 1mm spacers on the two faces of the inserted core and install the sec­ ond core half in place and secure it with a clip. You now have a finished inductor and it can be soldered into the main board either way around. The large finned heatsink on the rear panel is necessary to keep the output devices (Q1, Q2, D1 & D2) cool. Use cable ties to keep the wiring neat and tidy. Rear panel hardware Now insert the PC board into its correct position in the case and mark the centres for the power transistor and diode mounting holes on the rear panel. Remove the rear panel and drill out these holes plus two holes for the cord­ grip grommet and fuseholder in the position shown on the wiring diagram. Also 4mm holes are required for the transformer mounting and the earth termination plus the bridge rectifier which mounts above D1. Do not forget the holes to mount the thermal switch THS1. Holes for the transistors, diodes and rectifier must be deburred with a larger drill to pre­ vent punch-through of the insulating washers and to ensure a flat contact to the heatsink. Fig.3: the power transistors and power diodes are mounted as shown here. After mounting, use a multimeter to confirm that their metal tabs are indeed isolated from the rear panel. Place the heatsink against the rear panel and mark the hole positions on it for drilling. Note that you must line up the heatsink so that the screws for Q2, D1 and the rectifier pass through the heatsink between the heatsink fins. Drill out and deburr all the holes. Attach the PC board to the case with the supplied self-tapping screws. Ap­ ply a smear of heatsink compound to the flat face of the heatsink and secure each of the transistors and diodes to the rear panel and heatsink with a screw, nut, insulat­ing washer and in­ sulating bush. Fig.3 shows the details. If you use mica washers apply a smear of heatsink compound to the mating surfaces before assembly. The silicone impregnated washers do not require heatsink compound. Check that the metal tabs of the devices are indeed isolated from the case by measur­ing the resistance with a mul­ timeter. Apply a smear of heatsink compound to the face of the rectifier before securing it to the rear panel. It is not necessary to insulate the rectifier case from the rear panel. Fit the AC power cord into its cordgrip grommet and secure it into March 1998  49 Fig.4: this diagram shows all the details of the wiring from the PC board to the front and rear panels. Take care with the mains wiring and shroud all exposed mains terminals with heatshrink tubing. 50  Silicon Chip Fig.5: check your etched PC boards against these full-size artworks before mounting any of the parts. Below: the thermal cutout (THS1) is mounted on the rear panel above Q1, Q2, D1 & D2, along with the bridge rectifier and power transformer. March 1998  51 Parts List 1 PC board, code 14302981, 121 x 173mm 1 PC board, code 14302982, 29 x 16mm (required for SMD version of IC1) 1 front panel label, 244 x 75mm 1 plastic instrument case, 257 x 190 x 85mm 1 aluminium rear panel to suit above case 1 heatsink, 109 x 75 x 33mm (DSE H-3460 or equivalent) 1 18V 6A mains transformer (T1) (DSE M2000 or equivalent) 1 ETD29/16/10 transformer assembly with 3C85 cores (L1) (Philips 2 x 4312 020 37502 cores, 1 x 4322 021 34381 bobbin, 2 x 4322 021 34371 clips) 1 NTC thermistor (DSE R1797) (NTC1) 2 3AG panel mount safety fuse holders (F1,F2) 1 630mA slow blow 3AG fuse 1 7A fast blow 3AG fuse 1 SPST neon-illuminated mains rocker switch (S1) 1 SPDT centre-off toggle switch (S2) 1 DPDT toggle switch (S3) 1 4P3W rotary switch (S4) 1 2P6W rotary switch (S5) 1 80°C thermal cutout (THS1) 1 momentary pushbutton switch with normally open contacts (S6) 1 black 4mm banana panel socket 1 red 4mm banana panel socket 1 black 2mm micro banana panel socket 1 red 2mm micro banana panel socket 1 black 4mm banana plug 1 red 4mm banana plug 1 black 2mm micro banana plug 1 red 2mm micro banana plug 5 M4 screws x 10mm the rear panel hole. Also, secure the fuseholder and transformer with 4mm screws, star washers and nuts. Attach the earth wire (green/yellow stripe) to the solder lug or crimp lug and secure to the rear panel with a screw, star washer and nut. 52  Silicon Chip 6 M4 nuts and star washers 4 M3 screws x 10mm and nuts 1 M3 screw x 25mm and nut 4 self-tapping screws to mount PC board 4 insulating bushes for TO-220 and TO-218 packages 2 TO-218 insulating washers 2 TO-220 insulating washers 25 PC stakes 1 7.5A mains cord with 3-pin plug 1 mains cordgrip grommet 2 1mm spacers, 10 x 5mm, to gap L1 1 600mm length of red hookup wire 1 600mm length of green hookup wire 1 600mm length of blue hookup wire 1 600mm length of yellow hookup wire 1 600mm length of black hookup wire 1 300mm length of red heavy duty hookup wire 1 300mm length of black heavy duty hookup wire 1 150mm length of 0.8mm tinned copper wire 1 2m length of 1mm enamelled copper wire 1 55mm length of 15mm diameter heatshrink tubing 1 50mm length of 25mm diameter heatshrink tubing 7 small cable ties 1 solder lug for earth terminal 2 10-way single in-line pin headers (if IC1 is surface mount) 5 5mm LED bezels Semiconductors 1 TEA1102 or TEA1102T fast charge controller (IC1) 1 4093 quad Schmitt NAND gate (IC2) 1 4020 binary divider (IC3) Front panel details The front panel can now be drilled out to accept the switches, terminals, fuseholder and the LED bezels. The front panel artwork can be used as a template for drilling. Attach the label in place after drilling and cut out the 1 TIP147 PNP power Darlington transistor (Q1) 1 TIP142 NPN power Darlington transistor (Q2) 2 BC337 NPN transistors (Q3,Q5) 1 BC548 NPN transistor (Q4) 2 MUR1550 fast recovery diodes (D1,D2) 1 1N4004 1A diode (D3) 2 1N914, 1N4148 diodes (D4,D5) 1 35A 400V bridge rectifier (BR1) 1 12V 1W zener diode (ZD1) 1 11V 400mW zener diode (ZD2) 5 5mm red LEDs (LED1-LED5) Capacitors 1 1000µF 25VW PC electrolytic 1 100µF 25VW PC electrolytic 1 100µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 10µF 100VW MKT polyester (Philips 373 series) 1 3.3µF bipolar electrolytic 1 1µF 16VW PC electrolytic 1 0.1µF MKT polyester 1 0.0018µF MKT polyester 1 820pF MKT polyester or ceramic Resistors (0.25W 1%) 1 330kΩ 1 12kΩ 3 220kΩ 2 10kΩ 1 150kΩ 1 4.7kΩ 3 100kΩ 1 3.3kΩ 1 82kΩ 2 2.2kΩ 0.5W 1 68kΩ 2 2.2kΩ 4 33kΩ 2 1kΩ 1W 2 27kΩ 1 680Ω 2 22kΩ 1 68Ω 1 18kΩ 1 10Ω 1 15kΩ 2 0.1Ω 5W Miscellaneous Heatsink compound, solder, machine screws and nuts, etc. holes with a sharp hobby knife. The two rotary switches require their shafts to be cut down to about 12mm long, with a hacksaw. Their shaft rotation should be adjusted for only five positions for S5 and two positions for S4. This is done by (+) + + + + + Fig.6: this full-size artwork can be used as a drilling template for the front panel. FAST + + PROTECT REFRESH 6 + OUTPUT (-) THERMISTOR NO BATTERY 100% NICAD & NIMH + + + 12 7.2 9.6 (NICAD & NIMH ONLY) + + 2Ah 1.2Ah 14.4 + SLA (6V&12V) + 30 15 4Ah 60 Battery Capacity Mins TIMER BATTERY VOLTAGE REFRESH MULTI-PURPOSE FAST BATTERY CHARGER Testing Check your work carefully before doing any voltage tests. Then apply power and measure the voltage between the TP GND on the PC board and pin 12 on IC1. You should measure about +12V DC. Check that pin 14 and pin 16 of IC2 and IC3 are at +12V. Pins 1 & 16 should be at + 4.25V. Switch S3 to the NiCd & NiMH position and check that the “no battery” LED lights. Measure the output voltage on the plus and minus termi­ nals. It should measure about 10V on the 6V battery selection. When connecting the thermistor, check that the voltage at pin 8 of IC1 is at about +2V when the temperature is around 25°C. If you heat up the thermistor slightly by holding your finger and thumb tightly around its body, the voltage should drop. If the temperature rises, then it is either a very hot day and your body temperature is lower than that of the air or you have the wrong type of thermistor. When charging a battery, make sure you select the correct battery type and voltage on the front panel switches. Also set the timer for the closest timeout period for the particular battery capacity. If you are charging a lead-acid battery, the timeout set­ting does not matter. You may wish to check the charge current which should be made with an RMS meter or a digital oscil­ loscope which reads RMS. If a standard multimeter is used, you can expect the read­ing across the two 0.1Ω resistors in parallel to be about 200mV. An RMS reading should show about 300mV which is equivalent to 6A. To vary the current slightly, change the value of the 3.3kΩ resistor at the IB input of IC1; larger for less current, smaller for more. Note that the heatsink and Q1 will run hot on fast charge and so the charger should be provided with sufficient venti­ lation to prevent the thermal cutout operating. The TP CELL and TP GND PC stakes can be monitored to measure the cell voltage of the connected battery. Note: charging current is best determined by checking the charging time of a discharged battery. If it's too long, the current can be increased slightly by using a larger value resistor at pin 2 of IC1. A 3.9kΩ resistor will increase it by about 10%. If the charge time is too short, the battery may be suffering from memory effect. Try a few discharge & charge cycles. The timeout period can be increased to suit larger batteries by increasing the value of the 820pF oscillator capacitor. SC + FUSE (7.5A) + POWER 6V & 12V LEAD ACID NIMH, NICAD & SLA removing the locking collar from beneath the star washer and nut and rotating the switch fully anticlockwise. Now re-insert the locking washer into position five for S5 and position two for S4. Now assemble all components onto the front panel. Begin the wiring as shown on the diagram of Fig.4, using coloured hookup wire. The mains wiring must be done using mains rated wire. Be sure to sheath the terminals for the fuse and power switch with heatsh­rink tubing. Use heavy duty wir­ ing for the connections between the rectifier and PC board, the thermal switch and to the output terminals and fuse F2. Tidy up the wiring with cable ties and insert the front panel into the case with the LEDs protruding through their be­zels. You will need to make up some leads with banana plugs and alligator clips to connect from the output terminals to a bat­tery. Also, the thermistor connections require a lead with miniature banana plugs. We sheathed the thermistor wiring in heatshrink tubing. March 1998  53