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100W Digital Amplifier, Li-Po Battery . . . PortaPAL-D Powerful, Portable Public Address Loudspeaker System by John Clarke With battery operation, high efficiency loudspeakers and a class-D amplifier, the PortaPAL-D PA system has enough power to blow your socks off! It’s ideal for busking, sports events, meetings or anywhere you need a powerful, portable PA system. W hile we have published a portable public address loudspeaker system previously (also called the PortaPAL), that was more than 10 years ago, in February 2003. The main semiconductors used in that design have become unavailable and technology has marched ahead with efficient class-D amplifiers, along with the advent of lithium batteries which are much more energy dense. Our new PortaPAL-D uses the CLASSiC-D Amplifier published in November and December 2012, along with its matching speaker protector from the same months and the DC-DC Converter published in May 2013. With that combination we have a high-power amplifier that can be run from a 12V battery. One year later, we have added the preamplifiers, mixer, tone controls and power supervision necessary for the PortaPAL-D to function. We are using two 8 200mm loudspeakers (with concentric tweeters) 34  Silicon Chip in parallel to hand the full 100 watts available from the amplifier. Buying the commercial equivalent could easily set you back by more than a thousand dollars! The PortaPAL-D is in a timber cabinet measuring 620 x 350 x 330mm and weighing about 20kg. It is covered in speaker carpet with corner protectors, to guard against damage from bumps and roadie use. The two loudspeakers are mounted behind protective steel grilles that are themselves protected by being recessed into the box. On the rear is the main control panel, again recessed into the box for protection against damage. A top hat socket, for use with a speaker stand and a carry handle are included. The cabinet and chassis for the electronics can be made using standard tools. And you need not be worried by small imperfections while building the cabinet since these will be covered by the carpet anyway. The result will be a PA box that looks professionally finished. Sealed enclosure The cabinet includes an open section to mount the PortaPAL-D electronics but the rest of the box is an infinite baffle design. This has advantages over an open-back design in that the sealed cabinet provides damping of the speaker cone at low frequencies, preventing the cone from being overdriven with high power bass signals (or when accidentally dropping a microphone onto the floor!). Another advantage is that the microphone just needs to be positioned behind the front edge of the speaker cabinet to minimise acoustic feedback. Two XLR sockets are provided for balanced microphones with one channel providing phantom power, if required. Both inputs can be used with dynamic microphones. Guitar input is via a standard 6.35mm jack socket while RCA stereo sockets mix left and right line inputs into a mono signal. siliconchip.com.au PortaPAL-D Features • Class D low-distortion power amplifier delivering up to 100W to the loudspeakers • Portable 12V Li-Po batterypowered amplifier with charger • Twin 200mm loudspeakers with integral tweeters • Two microphone inputs (4.5mV) • Guitar input (50mV) • Line input (1V) and output • Individual level controls • Bass and treble controls • Standby power-down to conserve battery power • Low battery shutdown • Standby indication • Charger indication • Thermostat-operated air circulation fan • Rugged cabinet with carpet, corner protectors and speaker grilles • Top hat included for use with speaker stands Each input has its own level control and bass and treble tone controls are provided. A line output is also provided to feed an additional amplifier, recorder, etc. Power source & management The PortaPAL-D is powered via a 12V Lithium Polymer (Li-Po) battery rather than the sealed lead acid (SLA) type of the original PortaPAL. This makes it much lighter. While a typical 7.2Ah SLA battery will weigh 2.55kg, the much smaller 8Ah Li-Po is less than a third of this. Plus, the Li-Po battery can be discharged much more deeply before recharging. In effect, you get more than double the SLA’s capacity for a fraction of the weight and size. As well as a main power switch, a two-stage standby circuitry automatically powers down sections of the circuit to reduce power drain if the PortaPAL-D is not making noise. Two LED indicators show the standby status. siliconchip.com.au Power is restored quickly when an input signal is detected. A low-battery shutdown is also included which protects the battery from over-discharge. We estimate that the PortaPAL-D should run for at least eight hours with normal use and longer with periods of shutdown. A commercially-made charger (intended for Li-Po cells) is set into the front panel, so that its controls can be accessed and its status LED visible. This can be powered from a nominal 12V (11-15V) supply, with a current up to 4.5A if the supply can deliver that. The battery can be charged at any time, regardless of whether the PortaPAL-D is in use or even switched off. Typically a 12V plugpack would be used to charge the PortaPAL-D, although a larger battery could also be used, either free-standing or in a vehicle. Circuit overview Fig.1 shows the general arrangement of the PortaPAL-D. As already mentioned, we use the CLASSiC-D amplifier module, the loudspeaker protector and the DC-DC Converter published previously. Full details for these projects can be found in the November and December 2012 issues for the amplifier and protector and the May 2013 issue for the DC-DC Converter. They can also be accessed on-line via www.siliconchip.com.au. The CLASSiC-D amplifier is used mainly due to its efficiency (and therefore power saving). It can run at high power without generating too much heat. This is a distinct advantage December 2013  35 PROTECT LK4 SIGNAL CLASSIC-D AMPLIFIER IN MIXER AND PREAMPLIFIER SPEAKER OUT OUT (NOV/DEC 2012) LK3 IN 8 COAXIAL SPEAKERS LOUDSPEAKER PROTECTOR OUT (NOV/DEC 2012) +35V, 0V SHUTDOWN –35V +12V 0V CELL MONITOR CELL EQUALISATION – + Li-PO 3-CELL BATTERY 8Ah  Fig.1: the PortaPAL-D brings together several recent and quite innovative projects into one handy unit. The mixer and preamplifier sections are new and based on proven designs but the main amplifier, the CLASSiC-D 100W digital amplifier, the DC-DC converter which powers it and the loudspeaker protector which prevents catastrophic failure are state-of-the-art designs from the past twelve months. Also of note is the use of the 12V Lithium Polymer battery, saving significant weight and size, and the commercial Li-Po battery charger with added battery protection circuitry. DC-DC CONVERTER (MAY 2013) 50°C SWITCH + OUT Li-PO CHARGER FAN IN – CHARGER SUPPLY over conventional class AB amplifiers which are nowhere near as efficient and generate significant heat. Another reason is that the amplifier has proven reliable and has low levels of distortion and noise with extra features such as temperature cut out and over-current protection. The CLASSiC-D amplifier is powered by a DC-DC converter, delivering plus and minus 35V DC supply from a 12V supply. With this, it can deliver up to 100W into 4 for short periods and 50W on a continuous basis. CON3 MIC 2 IN GAIN IC1b Battery-saving auto shutdown To conserve battery when not actually being driven, the PortaPAL-D has a two-stage shutdown. First, after a short period of no signal, the amplifier module is shut down. This is controlled in part by the power supervision section. In the second stage, after a longer period of no signal, the power supervision circuitry VR1 BASS & TREBLE IC5b IC3a VR2 LEVEL + GAIN GAIN IC2 CON9 VR6 MIXER IC5a IC4a CON10 CON8 VR3 LINE INPUTS  SIGNAL DETECTOR (CON12) TO CLASS D AMPLIFIER ‘SHUTDOWN’ LED1 DELAY VR4 Q3, IC7, Q4 G S POWER LED3 POWER SUPERVISION (RELAYS 1-3) +12V TO PREAMPLIFIERS & MIXER 36  Silicon Chip RELAY4 IC6a, D1, D2, IC6b 10-WAY IDC CONNECTORS S1 SIGNAL OUT STANDBY1 LEVEL L R LINE OUTPUTS LEVEL + GAIN IC3b GUITAR INPUT switches off the DC-DC Converter and so powers down the system. The power supervision circuitry also controls the charging of the battery. While power is applied, the charger continually measures the voltage of each cell, ensuring each is not over- or under-charged. Typically, the lithium-polymer cell balancing leads would connect directly to the charger. However, this could mean the cells would discharge via the charger over time and possibly flatten the battery. To avoid this, we connect VR5 LEVEL + GAIN (CON10) GAIN IC1a 6-WAY SIL HEADER & SOCKET CON11 MIC 1 IN A small fan is switched by a thermostat when the amplifier heatsink reaches 50°C, circulating cooling air. (CON8) BATTERY LEADS +35V +12V SWITCHED POWER SUPERVISION  STANDBY2  LED2 Q5 D DC-DC CONVERTER +12V SWITCHER Fig.2: the circuit elements in more detail. These are explained in the text – and you can compare these elements with the circuit diagrams on following pages. siliconchip.com.au the cell monitor leads via the power supervision circuitry. Detail of the preamplifier, mixer and standby circuitry is shown in Fig.2. Microphone inputs (Mic1 and Mic2) and their gain stages (IC1a and IC1b) are on their own PCB and connect to the main PCB via a 6-way single in line (SIL) header and socket. The guitar input and line input plus the line outputs are also on a separate PCB and similarly connect via 10-way IDC socket and plug. The level potentiometers control the gain, with additional gain provided after the level controls for the microphone and guitar inputs. A mixer combines the four signals (Mic1, Mic2, Guitar and Line) and its output is fed to the bass and treble tone controls. From there the signal goes to the input for the CLASSiC-D amplifier, to the line outputs and also to a signal detector which forms part of the shutdown circuitry. In “Standby 1” state, if the signal is off for longer than 15s, relay 4 is triggered, shutting down the CLASSiC-D amplifier. The amplifier is still powered but in shutdown. LED1 lights to show this state. Any input signal will instantly restore full operation to the amplifier. If there is still no input signal af- PortaPAL-D Specifications Output Power: 100W into 4 short term 50W into 4 continuous Output sound level: Typically 96dB (SPL) at 1W Input sensitivity and Microphone: 4.5mV; <20Hz-20kHz Frequency Response (-3dB): Guitar: 50mV; 25Hz-25kHz Line: 1V; <20Hz-50kHz Tone Controls: Bass +11dB and -14dB at 100Hz Treble +9.5dB and -12.6dB at 10kHz Signal-to-Noise Ratio: -80dB with respect to 50W into 4 (inputs at minimum gain; 20Hz-20kHz bandwidth); Muting: Threshold at <150mW output power Standby modes (no input): 15s typical for Standby1 100s typical for Standby2 <1s return to normal operation Battery consumption: “Low battery” state activated – 8.5A Standby2 – 45mA (DC-DC converter turned off) Standby1 – 320mA (amplifier only turned off) Powered, before either standby state – 730mA “Low Battery” thresholds: Typically 10.5V switches PortaPAL-D off 11.2V switches PortaPAL-D on Battery Charger: Input 11-15VDC, 4.5A charging current maximum Dimensions: 620 x 350 x 330mm inclusive of corner protectors Mass: 17.5kg Here’s a view of the electronics module in its metalwork, removed from the PortaPAL-D speaker box. A commercial charger is incorporated because it is perfectly suited to the Li-Po battery pack we used and will result in longest battery life. siliconchip.com.au December 2013  37 +12V 4 4 +12V 10k* 10F* 10k* 10k* * THESE COMPONENTS FOR PHANTOM POWER MIC1 INPUT 1 3 2 CON1 1k FB° 1k 1 IC1a 3 47F FB° 2 470pF CON2 10k FB° MIC1 OUT SIGNAL GND 3 +Vref 150pF 3 1 IC1: LM833 22k °FERRITE BEADS 1 150 6 150pF Vref 22k 1k 6 7 IC1b 150 5 CON8 6 +12V POWER GND SIGNAL GND 6 2 x 47F 1k 3 10pF 2 CON4 7 6 IC2 LINE INPUTS R CON6 R LINE OUTPUTS SC 2013 10k PORTAPAL-D GND LINE IN MIC2 LEVEL 1F # VR2 10k LOG +12V 8 9 1 9 +Vref 10F 4 # LINE IN 2 LINE OUT 5 2.2F MICROPHONE, GUITAR & LINE INPUTS & OUTPUTS lights to show power is on. Main power is controlled via switch S1. If on, the battery voltage is monitored by the low voltage shutdown section (IC8 and Q1). Should the battery supply drop below about 10.5V, the power to the 330nF LINE OUT 1F VR3 10k LOG NP 5 GUITAR LEVEL 7 Vref Fig.3: the input circuitry for the two microphones, guitar (which of course could be used for other sources) and the line inputs (suitable for audio players such as MP3s or tablets) are quite conventional. Only Mic1 input has provision for microphones requiring phantom power but you can use ordinary (dynamic) mics on this input too. ter about 100s, “Standby2” state is entered. Power is switched off to the DC-DC Converter and this in turn switches off the CLASSiC-D amplifier, while LED2 lights showing Standby 2. When there is audio, power is restored to the amplifier within 1 second. LED3 38  Silicon Chip GND (10-WAY IDC CONNECTOR) L 6 3 +Vref 10F CON7 4 8 2.2k 10F CON10 +12V GUITAR IN 680pF 2.2k 1F # POT BODIES WIRED TOGETHER WITH 330nF TO EARTH (6-PIN SIL HEADER SOCKET) +Vref 1 7 2.2F MIC1 LEVEL VR1 10k LOG CON11 GUITAR IN 1M L 150 4 4.7k +Vref 10F 3 TP3 4.7k CON5 +12V 5 MIC2 10F 100nF IC2: TL071 7 4 # 2 150pF GUITAR INPUT 1 MIC1 (6-PIN SIL HEADER) 22k 10k MIC2 OUT CON3 4 47F 3 +Vref TP2 5 1k 100F 6 8 IC4b TP1 8 2 10k MIC2 INPUT 5 10k 47F 10k 10k POWER GND 22k 47F FB° 470pF 2 10F 100nF 150pF +12V # LINE IN LEVEL 10F VR4 10k LOG 2 (10-WAY IDC CONNECTOR) SC 2013 PORTAPAL-D preamplifiers and mixer is removed and the whole system shuts down. Current draw is only that of the low voltage shutdown circuitry at 8.5A. Circuit detail Balanced microphone inputs for Mic1 and Mic2 are via XLR sockets, with the signals fed to the inputs of low noise op amps IC1a & IC1b. Assuming 600 microphones, these preamplifiers have a gain of 22. Both are identical, except that the Mic1 input provides phantom power for electret microphones (if used). Phantom power is limited to 0.5mA or so, sufficient for the typical electret microphones used in PA systems siliconchip.com.au +12V 10F 100nF 150 100nF 1000F CHASSIS +Vref IC5: TL072 10nF 15nF 100pF 8 IC3a 2 10F 18k NP 2 3 TP4 10k 100k IC5a 4 NP TP7 CUT VR5 100k LIN 1k 10k TREBLE +Vref 8 IC5b 7 10F 10k CUT VR6 100k LIN x11 AMPLIFIER 47pF 6 5 1.5nF BOOST 330pF 10F BOOST 1F 1 30k 1k +Vref 1 15k 18k BASS 30k 3 100F 100nF OUTPUT TO AMPLIFIER CON9 10 LK1 10k 47k IC3: LM833 MIXER 5 100k 7 IC3b 6 4 15k TP5 10k 1k 100k IC4a 1 10k 15k TP6 330pF x11 AMPLIFIER 10k MIXER & TONE CONTROL SECTION (MAIN PCB) but not condenser microphones. If more current is required, reduce the 10kresistors, possibly to 2.2k or less. High frequencies above 48kHz are rolled off by the 150pF capacitors across the 22kfeedback resistors. The 470pF capacitor shunting the balanced input lines, in conjunction with the microphone impedance, also roll off the high frequencies. Ferrite beads in the 1k input resistors help to reduce RF pickup, while the use of 1% resistors in the balanced microphone circuits ensures good rejection of common mode signals such as mains hum. The unbalanced outputs are each siliconchip.com.au TO POINT A IN POWER SUPERVISION SECTION (SIGNAL DETECTION) To whet your appetite ready for the assembly details next month, this shot shows the internal make-up of the PortaPAL-D. At left (vertical) is the main CLASSiC-D amplifier board, while at top right is the mixer and tone control PCB. Below that is the mic, guitar and line input/ output board while the long blue object is the Li-Po battery. Its charger is the “black box” almost hidden at rear, along with the DC-DC converter in its own diecast case. IC4: LM833 2 +Vref Fig.4: from the audio input boards, signal is fed to level control pots, more amplification and thence to the mixer and tone control stages. The ouput from this goes to the CLASSiC-D digital amplifier. x11 AMPLIFIER 3 10F 150 330pF 10F 1k TONE CONTROLS fed to level potentiometers VR1 & VR2 via a 150 stopper resistor and 10F AC coupling capacitor. The signals are then applied to op amps IC3a and IC3b, both of which have a gain of 11. This means that maximum gain for microphone signals before the mixer is 242. Guitar input The guitar input stage comprises IC2, a TL071 Fet input op amp connected as a non-inverting amplifier with a gain of 2 for mid-band frequencies. The guitar signal is coupled via two 47µF capacitors in series. These are equivalent to a non-polarised capacitor and are included to cater for inputs with a positive or negative bias voltage, that goes beyond the voltage bias set by the Vref (at half supply). We have specified the high load resistance of 1M to ensure optimum high frequency response with the relatively high inductance of typical guitar pickups. With such a high load resistance, you might wonder why we have used such a large input coupling capacitance. After all, to maintain a flat response to below 20Hz, all you need is an 8.2nF input capacitor. The reason is to minimise noise, which occurs when op amp IC2 sees as low a source impedance as possible. Output from IC2 is coupled to the “guitar” level control, VR3, via a 150resistor and 10F capacitor. The December 2013  39 +12V FROM IC5b PIN 7 IN TONE CONTROL SECTION 100nF 10F LED1 K 3 8 1 IC6a 2 1k 1F A CHARGER OUTPUT CHARGER SUPPLY OUT CHARGER SUPPLY IN 220F 10F 1k 4 3 IC7 7555 6 2 10k 1M C B 10k B 100k SIGNAL DETECTOR 8 7 A 10F BATTERY 470k 470k K 22pF 1k A 7 IC6b 5 D1 1N4148 100F CON12 6 K 4 470k K D3 4.7k D2 1N4148 CLASS-D AMPLIFIER SHUTDOWN RLY4  470k TP9 DC-DC CONV MAIN SUPPLY A STANDBY1 IC6: LM358 A +12V’ 10 SCHMITT TRIGGER C 1 Q3 BC337 K E Q2 BC337 A E 10k D4 1N4148 DELAY CON13 + – + – + – + – + – 4 5 7 L1 16H 1 2 10A 8 9 10 S1 CHASSIS RLY1 o 11 K POWER D6 1N5404 12 13 RLY2 K 50 THERMAL CUT-IN (NO) – 3 2 3 2 CELL SENSING RLY3 A 4 D1– D4: 1N4148 A 1 CON14 270k Li-PO 3-CELL BATTERY CON15 4 2.2M 12V FAN + 1 D5 1N4004 270k  + A – CHARGE SENSE INPUTS (CON13) F1 6 SC  2013 PORTAPAL-D K 1N4004 POWER SUPERVISION SECTION (MAIN PCB) A K Fig.5: here’s where the PortaPAL-D excels over earlier mixers – it uses a Li-Po battery and a commercial charger to give much more “bang for buck” when it comes to portable use. For a full explanation, see the accompanying text. signal is then fed to op amp lC4a, which is identical to IC3a & IC3b. Line signal Stereo line inputs (eg, from a CD player or MP3 player) are mixed to a mono signal with 2.2k resistors and fed to potentiometer VR4 via a 2.2F coupling capacitor. Signals from all four input sources are mixed via 15k resistors for the mic and guitar signals and a 10k resistor for the line signal in inverting amplifier IC5a. This has a gain of minus two for the first mic and guitar signals, with slightly higher gain for the line input signals (due to the 10kresistor 40  Silicon Chip to compensate for a slight gain loss in the resistive mixing of the stereo line inputs). IC5a drives the tone control stage comprising IC5b, VR5 and VR6 and associated resistors and capacitors. IC5b’s output signal is fed to three separate places; the line output via RCA and 6.35mm jack sockets, the signal detection stages involving IC6a and the input to the CLASSiC-D power amplifier. All of the op amps in the circuit used as signal amplifiers are biased via the Vref line, which is at half supply (about +6V). This is derived from the +12V line by a voltage divider consisting of two 10k resistors with the centre point bypassed by a 100F capacitor. The bypassed supply is then buffered by op amp IC4b to provide the Vref line. All these biased op amp outputs will sit at about half the battery voltage, with the audio signal rising and falling about this DC voltage Shutdown As noted above, we have incorporated signal detection into the circuit to shut down the power amplifier in order to reduce current consumption when no signal is present. Op amp IC6a is a non-inverting amplifier with a gain of 471, set by the 470k and siliconchip.com.au 5 +12V’ A +12V STANDBY2 LED2  K 10k Q5 IRF9540 4.7k S G 10k D 10k B A POWER  C Q4 BC337 E LED3 3 (CON13) K TO DC-DC CONVERTER SWITCHED INPUT 4.7k +12V 2200F 25V 1F MMC LOW ESR 2 3 S +12V’ Q1 IRF9540 G 8 V+ HYST D 100k 100k 4 IC8 OUT MAX8212 THRESH GND 5 LOW VOLTAGE SHUTDOWN BC337 B LEDS E K A C IRF9540 1N5404 G A K D D S 1kfeedback resistors. The 22pF capacitor rolls the gain off above 15kHz, while the 10F capacitor in series with the 1k resistor rolls off signals below 15Hz. The amplified signal from IC6a is then fed to a diode pump circuit consisting of diodes D1 & D2 and the 1F & 10F capacitors connected to them. Peak level of the signal from IC6a will be stored in the 10F capacitor which is continuously being (slowly) discharged via the 1M resistor across it. IC6b, connected as a Schmitt trigger inverter, monitors this voltage. A 470k resistor between pin 5 and pin 7 applies positive feedback siliconchip.com.au to give hysteresis. This makes the comparator output switch cleanly between high and low, and to prevent oscillation at the switching threshold. The inverting input of IC6b is set at +2.1V (ignoring the effect of the 470kfeedback resistor) using the 470kand 100kresistors across the 12V supply. When power is first applied to the circuit, the 10F capacitor between the 12V supply and the inverting input to IC6b is initially discharged and therefore pulls pin 6 low, causing the output (pin 7) to be high. This turns on transistor Q2, so relay 4’s contacts close and the CLASSiC-D amplifier is shut down. At the same time, transistor Q3 is turned off so IC7’s inputs (pins 2 and 6) are high due to the 220F capacitor connecting to the 12V supply being initially discharged. The output (pin 3) is low so Standby 2 LED (LED2) is lit. The low output holds both Q4 off and Mosfet Q5 off. This removes power from the DC-DC converter switch and as a result the CLASSiC-D amplifier is off. When audio signal is detected by IC6b, the input (pin 6) will go above the 2.1V at pin 5 so the output (pin 7) goes low, switching off Q2 and the relay. Diode D3 quenches the backEMF of the collapsing relay coil field . There is still a low current flow through the relay coil and Q3 – not enough to pull the relay in but enough to turn Q3 on. This provides a path to ground (via the 1k resistor) which charges the 220F capacitor. The now-low input to the 7555 cause its output (pin 3) to go high, switching on power LED (LED3) and transistor Q4 and switching off the Standby 2 LED. Mosfet Q5 also switches on and the DC-DC Converter is powered, in turn powering the CLASSiC-D amplifier. Low battery Regardless of the battery type, it is important that it not be over-discharged and permanently damaged. While the Lithium-Polymers used in the PortaPAL-D are better than SLAs in this regard, care still needs to be taken. Low battery voltage is detected using IC8, a micropower voltage monitor that compares the voltage at pin 3 to an internal 1.15V reference. With a 12V supply, the voltage divider across IC8s input will ensure that pin 3 is always above 1.15V. However, as the battery discharges, this voltage will drop. Below 10.5V, IC8s output (pin 4) will go high, turning off Mosfet Q1. This removes power from the rest of the circuit thus preventing the battery being discharged any further. Pin 2 provides hysteresis, stopping the circuit oscillating back and forth around the 1.15V threshold. While ever the voltage at pin 3 stays above 1.15V, pin 2 is effectively connected to the supply rail, thus shorting out the 270k resistor to 12V. However, if the pin 3 voltage drops below 1.15V pin 2 is effectively open circuit. So that extra 270k resistance is added to the voltage divider, which drops the voltage at pin 3 even lower (just over 1V with a 10.5V supply). Therefore the battery needs to be charged to more than 11.6V before the output (pin 4) goes low, allowing the Mosfet to power the circuit again. Power Power from the battery passes through the 10A fuse, F1 and power switch S1. Inductor L1 and the 2200F capacitor filter the supply, helping prevent DC-DC converter switching noise from entering the supply for the audio op amps. Additional filtering is provided with the 10 resistor and the supply decoupling capacitors on the 12V rail. Note that the high current supply required by the DC-DC Converter is tapped off before the switch. Only the low power switching current to control the DC-DC Converter is at the output to Q5. Reverse polarity protection is via diode D6: this will blow the fuse if the supply polarity is inadvertently connected back to front. Charging Three relays are used to switch in the charger connections. The supply to the charger is tapped at pins 10-13 of CON13 so that when power is available, relays (Relay1, Relay2 and Relay3) will be switched on. The charger output is switched to the battery positive via relay 1 contacts while the cell balancing outputs from the battery are connected to the charger via relay 2 and relay 3 contacts. When there is no power applied to the charger input, the relay contacts open and completely disconnect the charger from the battery. December 2013  41 PortaPAL-D – Parts List Main PCB (Mixer and power supervision) 1 PCB coded 01111131, 212 x 100mm 1 10-way IDC PCB mount socket (CON10) 2 10-way IDC line plugs 1 100mm length of 10-way IDC cable 1 6-way SIL socket (CON11) 1 2-pin header, 2.54mm spacing (LK1) 1 2-pin polarised header, 2.54mm spacing (CON12) 2 2-way pin header sockets 1 jumper shunt 6 DIL8 IC sockets (optional) 2 M205 PCB fuse clips 1 M205 10A fast blow fuse (F1) 1 iron powdered toroid 28 x 14 x 11mm [Jaycar LO1244] L1 5 2-way PCB mount screw connectors (5.08mm pin spacing) (CON13) 1 3-way PCB mount screw connectors (5.08mm pin spacing) (CON13) 1 vertical PCB mount RCA socket (CON9) 2 RCA line plugs 1 12V 10 or 16A SPDT relay [Altronics S4197, S4170A, Jaycar SY-4050] (RELAY1) 2 12V 1A DPDT relays] Altronics S4150, Jaycar SY-4059] (RELAY2,RELAY3) 1 12V SPST DIL reed relay [Altronics S4101A, Jaycar SY-4032] (RELAY4) 4 16mm single PCB mount 10klog potentiometers and nuts (VR1-VR4) 2 16mm single PCB mount 100klinear potentiometers and nuts (VR5,VR6) 6 knobs to suit above potentiometers (4 blue, 2 grey) 3 M3 tapped spacers 15mm long 1 solder lug 4 M3 x 10mm machine screws 2 M3 x 15mm machine screws 6 pot nuts (providing for an extra nut under potentiometer) 1 3S 250mm 2xJST-XH parallel balance lead [http://hobbyking.com.au/hobbyking/store/__32036__JST_ XH_Parallel_Balance_Lead_3S_250mm_2xJST_XH_.html] 1 1.5m length of 1mm diam. enamelled copper wire for L1 1 150mm length of 7.5A rated green hookup wire 1 150mm length of single core screened cable 1 270mm twin figure-8 light gauge wire 1 190mm length of 0.7mm diam. tinned copper wire 1 100mm cable tie 2 PC stakes Semiconductors 2 LM833 dual low noise op amps (IC3,IC4) 1 TL072 dual op amp (IC5) 1 LM358 dual op amp (IC6) 1 7555 CMOS 555 timer (IC7) 1 MAX8212 voltage monitor (IC8) 2 IRF9540 P-channel Mosfets (Q1,Q5) 3 BC337 NPN transistors (Q2-Q4) 4 1N4148 diodes (D1-D4) 1 1N4004 1A diode (D5) 1 1N5404 3A diode (D6) 3 3mm high brightness LEDs (LED1&2 [red]; LED3 [green]) 42  Silicon Chip Capacitors Electrolytic (PC type) 1 2200F 25V low ESR 1 1000F 16V 1 220F 16V 3 100F 16V 12 10F 16V 1 10F NP 50V 1 2.2F NP 50V 4 1F 16V 1 1F 50V NP MKT polyester 1 330nF 4 100nF 1 15nF 1 10nF 1 1.5nF Ceramic 1 1F monolithic multilayer (MMC) 3 330pF    1 100pF 1 47pF 1 22pF Resistors (0.25W, 1%) 1 2.2M 1 1M 4 470k 2 270k 6 100k 1 47k 2 30k 2 18k 3 15k 15 10k 3 4.7k 7 1k 2 150 2 10 Guitar input, line input and output PCB 1 PCB coded 01111133, 109 x 35mm 2 PCB mount 6.35mm switched jack sockets (CON4,CON7) 2 stereo RCA vertical stacked PCB mount (CON5,CON6) 1 10-way IDC PCB mount socket (CON8) 1 DIL8 IC socket (optional) Semiconductors 1 TL071 single op amp (IC2) Capacitors Electrolytic (PC type) 2 47F 16V 2 10F 16V 1 100nF MKT polyester 1 2.2F 16V PC 1 680pF ceramic Resistors (0.25W, 1%) 1 1M 1 10k 2 4.7k 2 2.2k 1 10pF ceramic 1 1k 1 150 Microphone input PCB 1 PCB coded 01111132, 64 x 73mm 2 PCB mount XLR female connectors [Altronics P 0883] (CON1,CON2) 1 right angle 6-way pin header with backing plate removed (CON3) 1 chassis mount 6.4mm spade terminal 1 female spade 6.4mm quick connector 4 ferrite beads 4mm ID x 5mm long [Jaycar LF-1250 or equivalent] 1 DIL8 IC socket (optional) 4 4g x 6mm self tapping screws or M3 x 6mm screws 1 M3 x 10mm machine screw 1 M3 nut 2 3mm star washers Semiconductors 1 LM833 low noise dual op amp (IC1) Capacitors 4 47F 16V PC electrolytic 1 100nF MKT polyester 4 150pF ceramic 2 10F 16V PC electrolytic 2 470pF ceramic Resistors (0.25W, 1%) 4 22k 7 10k 4 1k 2 150 siliconchip.com.au Extras 1 CLASSiC-D amplifier set for a ±35V output (see SILICON CHIP November & December 2012) 1 speaker protector for the CLASSiC-D set for a 35V supply (see SILICON CHIP, November/December 2012) 1 50°C NO thermostat (Jaycar ST-3831) 1 10F 16V PC electrolytic capacitor (used in speaker protector) 1 DC-DC Converter for the CLASSiC-D (see SILICON CHIP, May ’13) 1 10k0.25W 1% resistor (used in DC-DC converter) 1 Li-Po 11.1V battery (ZIPPY Flightmax 8000mAh 3S1P 30C) (http://hobbyking.com.au/hobbyking/store/__19530__ZIPPY_ Flightmax_8000mAh_3S1P_30C_AUS_Warehouse_.html) 1 HobbyKing E4 Li-Po balance charger (http://hobbyking.com.au/hobbyking/store/__14633__ HobbyKing_E4_Balance_Charger.html) 1 Polymax 5.5mm Gold Connector plug and socket set [Jaycar KG55001 set of 10 but only one plug and one socket required] (http://hobbyking.com.au/hobbyking/store/uh_viewitem. asp?idproduct=18659) 1 strap handle [Jaycar HS-8022, Altronics C 3660] 1 1.8m x 3m speaker box carpet [Jaycar CF-2755] 8 corner protectors [Jaycar HM-3843 (or HM-3829 – pack 8), Altronics C 3620 or C 3623] 1 speaker box “top hat” mount [Jaycar HS-8035, Altronics C 3602] 2 200mm speaker grilles [Jaycar AX-3594, Altronics C 3708] 2 8 200mm coaxial speakers [Altronics C 2005] 1 40mm 12V fan [Jaycar YX-2502, Altronics F 0010] 1 SPST mini rocker switch (S1) 2 9mm M3 tapped standoffs (for fan) 2 M3 x 10mm countersunk screws (for fan mounting standoffs to chassis) 2 M3 x 15mm machine screws (for fan mounting to standoffs) 1 solder lug 1 “P” cord clamp with M3 x 10mm screw, nut and washer 2 6.4mm crimp female spade connectors 1 200mm length of 10mm diameter heatshrink tubing (for covering charger and battery bracket) 1 red right angle banana plug [Jaycar PP-0394] 1 black right angle banana plug [Jaycar PP-0395] 1 2.5mm DC panel connector 1 2.5mm DC line plug 2 aluminium sheets 295 x 295mmm, 1mm gauge [Jaycar HM-9500] 1 350mm length of 12mm x 3mm aluminium 6 M3.5 tapped right angle (RA) bracket standoffs [Jaycar HP-0872] 16 M3 x 10mm machine screws (for mounting PCBs to chassis RA brackets to chassis – see note in construction article) 7 M3 x 15mm machine screws (3mm aluminium brackets to RA brackets, through 12mm standoffs on brackets 3mm aluminium to standoffs) 1 M3 x 20mm machine screw 10 M3 x 6mm countersunk screws (DC-DC Converter mounting, battery and charger brackets, RA brackets to chassis) 12 M3 nuts (RA brackets) 2 small cabinet handles (45mm long x 15mm high x 6mm wide or similar) (optional) 1 2-way 15A terminal strip (optional for extension speaker) 1 1m length of 7.5A figure-8 wire for speaker connections 3 1m lengths of 7.5A hookup wire (1 each red, black, green) 2 25mm length of 6mm heatshrink tubing (1 each red & black) 2 25mm length of 10mm heatshrink tubing (1 each red & black) 2 100mm cable ties Box Hardware 8 8g 12mm panhead wood screws (for speaker mounting) 24 6g 16mm countersunk wood screws (bronze) (for attaching corner protectors) 5 4g x 16mm panhead screws (for mounting the chassis to the cabinet) 1 500ml tin of contact adhesive 2 strips of putty adhesive (eg, Blu-Tack) 2 cushion bags of polyester wadding (eg, Innerbond) 1 3m length 18mm x 18mm DAR (dressed all round) pine 1 6m length 12mm x 12mm DAR pine 2 900mm x 600mm x 16mm sheets of MDF (or single 1800 x 600mm x 16mm sheet ) Resistor Colour Codes Total No. Value o 1 2.2MΩ o 2 1MΩ o 4 470kΩ o 2 270kΩ o 6 100kΩ o 1 47kΩ o 2 30kΩ o 1 27kΩ o 4 22kΩ o 2 18kΩ o 3 15kΩ o 22 10kΩ o 4 4.7kΩ o 2 2.2kΩ o 12 1kΩ o 3 150Ω o 2 10Ω siliconchip.com.au 4-Band Code (1%) red red green brown brown black green brown yellow violet yellow brown red violet yellow brown brown black yellow brown yellow violet orange brown orange black orange brown red violet orange brown red red orange brown brown grey orange brown brown green orange brown brown black orange brown yellow violet red brown red red red brown brown black red brown brown green brown brown brown black black brown 5-Band Code (1%) red red black yellow brown brown black black yellow brown yellow violet black orange brown red violet black orange brown brown black black orange brown yellow violet black red brown orange black black red brown red violet black red brown red red black red brown brown grey black red brown brown green black red brown brown black black red brown yellow violet black brown brown red red black brown brown brown black black brown brown brown green black black brown brown black black gold brown Capacitor Codes Value F Value IEC Code EIA Code 330nF 0.33F 330n   334 100nF 0.1F 100n   104 15nF 0.015F 15n   153 10nF 0.01F 10n   103 1.5nF 0.0015F 1.5n   152 680pF NA 680p 680 470pF NA 470p 470 330pF NA 330p 330 150pF NA 150p 150 100pF NA 100p 100 47pF NA 47p 47 22pF NA 22p 22 10pF NA 10p 10 NEXT MONTH: We’ll present Part 2 with all the construction details, including making & wiring the electronics. SC December 2013  43