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Tim Blythman’s Dual-Channel Power Supply for BREADBOARDS Things can get messy when you’re prototyping a design on a breadboard but you definitely don’t want to make a mistake hooking up the power supply! This Dual-Channel Breadboard PSU is the perfect solution. It plugs straight into a breadboard’s power rails, has two adjustable current-limited outputs and can run from different power sources. It has already become an indispensable part of our workbench. W e do a lot of prototyping on breadboards. It’s the easiest way to test ideas, especially if you need to try out tweaks and modify a circuit configuration. Jumper wires make it nice and easy to wire up a circuit and make changes on a solderless breadboard. While you can get compact power supply modules that plug straight into a breadboard and provide 5V and 3.3V rails, like Jaycar Cat XC4606 and Altronics Cat Z6355, they have their drawbacks. The main problems are that they only offer one voltage at a time and lack the flexibility and current-limiting features of a bench power supply. So we decided to design a low-cost, easy-to-build replacement incorporating the most important features of a bench supply. The result is a Breadboard PSU that’s versatile yet straightforward. It plugs directly into a breadboard’s power rails at one end, like the simpler supplies described above, but it has two independent outputs. We have published a similar design called the Arduino-based Power Supply (February 2022), a compact solution for a home workshop. Like this Breadboard PSU, it provides up to 14V output at up to 1A, although it only has one output. As the Arduino-based Power Supply is controlled by a computer, it Practical Electronics | December | 2023 can be tucked away. Its controls and display are displayed on the computer screen, so it does not take up any more valuable workbench space. But there is nothing quite so tactile as being able to adjust a couple of knobs to dial in voltage and current settings while you’re testing a prototype, and that is how the Breadboard PSU works. If you’re working close-up with the breadboard, having the supply controls nearby is convenient, and the PSU doesn’t make the whole breadboard set-up much bigger. Two independent output channels Most breadboards have at least two sets of supply rails, one pair on either side. Given that, and the fact that many circuits require two voltages (eg, 3.3V and 5V or 5V and 12V), adding a second channel seemed like a great idea. Even just using the two outputs as independent, current-limited supplies at the same voltage can be very handy for testing and validating parts of a circuit. Despite duplicating much of the circuitry, we’ve managed to keep the end result compact. The basic version doesn’t even have a display; it just has four knobs to dial in the voltage and current limit on each of the two channels. It is certainly usable on its own, but there are evident benefits to being able to see the output voltages and currents as you work on your prototype. Later, we will present a neat little display module that not only provides readouts for the Breadboard PSU but also offers extra measuring channels to help you see what else is happening on your breadboard. A particularly handy facility Features and Specifications ∎ Two independent channels ∎ Each channel delivers 0-14V/0-1A (depending on input supply and load) ∎ Runs from 7-15V DC or USB 5V DC ∎ Plugs straight into breadboard power rails ∎ Four potentiometers provide all controls ∎ Optional metering add-on described on page 34 (shown above) ∎ Transient load regulation: <80mV DC + 350mV AC, 0-1A ∎ Transient settling time: 300µs, 0-1A 25 Breadboard Power Supply – Main Board Circuit Circuit operation For the most part, the two channels of the Breadboard PSU have identical circuits that work independently. Having said that, they are supplemented by some common supply circuitry, as shown in Fig.1, the full circuit diagram. You might notice that there are no regulator ICs in the main part of the circuit, at lower left. Instead, like the earlier Arduino PSU, the two outputs have their voltage regulated by op amps controlling NPN emitter-­ follower transistors (Q1 and Q3). The op amps use negative feedback to adjust the transistor base voltages 26 to maintain the desired output voltages. This method of regulation can be a bit tricky due to the need for it to respond fast to changes in output load while at the same time, needing stability to avoid oscillation. Luckily, by using NPN emitter-followers, we avoid a large phase shift and gain a great deal of ‘local feedback’, so the op amps only need to make minor adjustments. More on that local feedback later. As the supply is intended to be flexible, there are two different ways to power it. We’ll refer to the higher of these as 15V but its absolute maximum is 16V, the highest voltage that all circuit components can tolerate. Apart from this, its exact value is not critical and we expect users will stick to around 12-15V DC, as supplies delivering that range of voltages are pretty common. Since the highest possible output voltage is around 2V below this rail, even a 9V battery is a valid option if you only need voltages up to about 5V. For example, if you are working primarily with microcontrollers. A 5V rail also exists in the circuit for components that cannot handle 15V. JP1 and JP2 provide the means to configure the sources of the 15V and 5V rails, respectively, and are Practical Electronics | December | 2023 Breadboard power modules like this are available from Jaycar and Altronics. They are inexpensive, convenient and can provide 5V and 3.3V rails as set by a switch, but they only supply one voltage at a time and don’t have adjustable voltages or current limiting. of each channel plus optionally two other currents across pairs of points located on the breadboard. Fig.1: the Breadboard PSU shares some circuitry with the Arduino Programmable Power Supply but with no microcontroller in sight. Instead, four potentiometers provide control of two independent current-limited adjustable supplies. derived from DC input jack CON1 and USB socket CON2. The incoming DC voltage at CON1 passes through reverse-polarity protection diode D1 to one side of JP1, allowing direct use of the incoming voltage for the 15V rail. The incoming DC at CON1 also feeds 78L05 linear regulator REG1, accompanied by an input bypass capacitor to produce a 5V rail, which goes to one side of JP2. With JP1 and JP2 set to the ‘REG’ and ‘JACK’ positions, the power from CON1 supplies all the power rails on the Breadboard PSU. When JP1 and JP2 are set to the alternative ‘BST’ and ‘USB’ positions, Practical Electronics | December | 2023 the 15V rail is derived from MOD1, an MT3608 boost module, which is supplied by 5V from the USB socket. The boost module has an adjustable output which must not be set any higher than 16V. Other components common to the two supplies are a 51kΩ/10kΩ divider which provides a scaled version of the 15V DC rail to a pin on CON5 for external monitoring. A four-channel INA4180A1 current shunt monitor (IC1) and its 100nF bypass capacitor are also shared between the two channels. It is powered from the 5V rail and used to monitor the output current Dual independent regulators The remaining circuitry is independently allocated to one of the two channels and identical between the two. Therefore, we’ll describe the function of one channel, with designations in brackets to indicate the equivalent part for the other channel. 10kΩ potentiometers VR1 (VR2) and VR3 (VR4) are wired across the 5V rail to set the voltage and current targets, respectively. The control voltage from VR1 (VR2) passes through a 100kΩ resistor and is filtered by a 100nF capacitor to reject noise, while the current control voltage goes directly to its own 100nF capacitor. These feed pins 3 and 6 of dual rail-to-rail op amp IC2 (IC3), respectively. The 16V supply limit of the op amps dictates the maximum of 16V the design can handle. IC2 (IC3) has a 10μF capacitor between its pin 4 and 8 supply pins, as its outputs can be expected to deliver a reasonable amount of current in sympathy with the PSU’s load. Its supply comes from the 15V rail and circuit ground. The voltage at pin 3 is compared with that at pin 2, which comes from a 51kΩ/10kΩ divider across output connector CON3 (CON4). This is fed from the emitter of MJE3055 NPN power transistor Q1 (Q3) via a 100mΩ current-­sense resistor. Q1’s (Q3’s) base is fed current from IC2’s (IC3’s) pin 1 output via a 100Ω resistor, filtered by a 10μF capacitor to ground. This low-pass filter works to prevent any oscillation that might occur. Q1’s (Q3’s) collector connects directly to the 15V rail. With Q1’s (Q3’s) base voltage held steady by the 10μF capacitor, if the output voltage at its emitter drops, the base-emitter voltage inherently rises, causing it to conduct more current and ‘prop up’ the output. Similarly, if the output voltage rises, its base-­ emitter voltage drops, so it conducts 27 The Breadboard PSU is designed to tap into small breadboards with longitudinal power rails, such as the Jaycar Cat PB8820 seen earlier. One end rests on header pins in the breadboard, while the other stands on tapped plastic spacers. less, moderating the output voltage. This local feedback provides fast corrections in response to load changes, keeping the output voltage reasonably steady in the short term. Slower corrections to its base drive from the Parts List – Dual-Channel Breadboard PSU 1 double-sided PCB coded 04112221, 99mm x 54mm, available from the PE PCB Service 1 PCB-mounting 2.1mm inner diameter barrel socket (CON1) 1 SMD mini-USB socket (CON2) 2 2-way pin headers, 2.54mm pitch (CON3, CON4) 2 6-way female socket headers (CON5, CON6) 3 3-way female socket header (CON7-CON9) 2 3-way pin headers with jumper shunts (JP1, JP2) 2 12mm-long M3-tapped spacers 4 M3 × 8mm machine screws 2 M3 hex nuts 2 M3 shakeproof washers 2 small TO-220 finned heatsinks (no larger than 20 × 20 × 10mm) 1 MT3608 boost module (MOD1) [SC4437] 4 10kΩ 9mm linear potentiometer and knobs to suit (VR1-VR4) [Jaycar RP8510 and HK773x] 4 short component lead off-cuts or pieces of wire (for mounting MOD1) Semiconductors 1 INA4180A1IPWR quad current shunt monitor, TSSOP-14 (IC1) 2 LMC6482 dual rail-to-rail CMOS op amps, DIP-8 (IC2, IC3) 1 1N4004 400V 1A diode (D1) 2 MJE3055 60V 10A NPN transistors, TO-220 (Q1, Q3) [Jaycar ZT2280] 2 BC547 45V 100mA NPN transistors, TO-92 (Q2,Q4) [Jaycar ZT2152] 1 78L05 5V 100mA linear regulator, TO-92 (REG1) [Jaycar ZV1539] Capacitors (all SMD M3216/1206 X5R/X7R or MKT/ceramic radial) 8 10μF 16V 7 100nF 50V 4 1nF 50V Resistors (all 1/4W axial 1% metal film except as noted) 3 51kΩ 7 10kΩ 2 100Ω 4 100kΩ 2 100mΩ M6432/2512 1W SMD 28 op amp provide longer-term fine-tuning to improve regulation. IC2a (IC3a) effectively tries to keep pins 2 and 3 at the same voltage by changing its output at pin 1. The voltage applied to CON3 (CON4) is thus a scaled version of the voltage on IC2a’s (IC3a’s) pin 3 with a low source impedance, forming the voltage control portion of the circuit. For the most part, the output voltage is proportional (as per the 51kΩ/10kΩ divider) to the voltage set by the voltage at the wiper of VR1 (VR2), but it can vary, as we shall see shortly. The 100nF capacitor across the 51kΩ feedback resistor helps the circuit respond quickly to changes by applying the full output voltage change to pin 2 of IC2a (IC3a) initially, rather than a scaled version. The 1nF capacitor between pins 1 and 2 of IC2a (IC3a) prevents oscillation by effectively increasing negative feedback at higher frequencies. The 100mΩ shunt mentioned earlier connects to pins 12 and 13 (2 and 3) of IC1, the current shunt monitor. IC1 is an amplifier that produces a voltage at its pin 14 (pin 1) that is 20 times the difference between its input pins. This voltage passes to IC2b’s (IC3b’s) pin 5 non-inverting input via a 10kΩ resistor. The shunt will induce a drop of 100mV at 1A which, when amplified by 20 by IC1, gives 2V/A at its output. The current setting voltage from VR3 (VR4) is directly connected to pin 6 of IC2b (IC3b), the inverting input, and the output from pin 7 drives the base of NPN transistor Q2 (Q4) via a 100kΩ resistor. Q2’s emitter is grounded and its collector connects to IC2’s (IC3’s) pin 3, the voltage setting. An excessive output current causes IC2’s (IC3’s) pin 5 to rise above its pin 6 voltage, so output pin 7 goes high to turn on Q2 (Q4), pulling down the voltage reference until the current limit is no longer exceeded. Another 1nF capacitor between IC2’s (IC3’s) pins 6 and 7 helps to reduce oscillation in the current control feedback loop, similar to the one in the voltage feedback loop. Theoretically, the default circuit values correlate to a full-scale voltage setting of 30.5V on VR1 (VR2) and about 2.5A on VR3 (VR4), but we don’t expect either of these will be achieved in practice. The dividers have mainly been selected so that the feedback and control voltages are below 3.3V, so an external monitoring circuit with a 0-3.3V input range can be used. Practical Electronics | December | 2023 timebase = ms Scope 1: the response to a load change that triggers current limiting is about as fast as possible given the size of the output capacitor. The 23.5W load brings the output voltage down from 12V to 10V at around 400mA. If REG1 were replaced with a pin-compatible 3.3V type (that can withstand an input of at least 16V), the maximum voltage and current settings would be 20V and 1.65A. This would have the advantage of making the controls less sensitive, so accurate adjustments could be made more easily. Supply options Feeding in 12-15V DC to CON1 will give the best results, as the 5V output of REG1 will be better regulated than the 5V DC from a USB power supply. While the USB option is convenient, the boost module could impose a high current draw on the USB supply, which might cause unexpected glitches if it is overloaded. If you only ever plan to feed in power via CON1, you could omit the USB socket and MOD1 and hard-wire the two jumpers. The remaining connectors, CON5CON9, are not needed when the Breadboard PSU is used in its standalone configuration, but can be used to connect to the display daughterboard, to be described on page 34. If fitting these connectors, use header sockets. These not only match up with the headers on the display board, but they also make it easy to use standard breadboard jumper wires to connect these points to your breadboard circuit. If you wish to tap into them for other purposes, CON5 and CON6 connect to most of the low-voltage signals mentioned earlier. CON7 provides breakouts for the incoming supplies from CON1 and CON2. CON8 and CON9 connect to the two spare current shunt monitor channels on IC1. Practical Electronics | December | 2023 timebase = sec Scope 2: the slowest response under any situation is shown here, where the output voltage is instantaneously set to 0V with no load. The drop rate is limited by the output capacitor discharging through the output voltage divider. Performance As the Breadboard PSU is based heavily on the circuit of the Arduino PSU, we knew it would work well. Still, we have produced a few scope grabs to give you an idea of what to expect. The response to a current limiting event is critical to any bench supply’s performance. Scope 1 shows the Breadboard PSU’s output using our Arduino Programmable Load (June 2023) to apply a step load change from an open circuit to 23.5Ω, with an initial voltage of 12V. The blue trace is the voltage and the red trace is the current, peaking at around 500mA. As you can see, the Breadboard PSU starts reacting almost immediately and has settled to the new operating point after about 150μs. Note that the time constant of the 10μF output capacitor into a 23.5W load is about the same duration, so most of the delay is actually due to the output capacitance discharging. Scope 2 shows a step change in the voltage setting from 12V down to 0V (applied by shorting the wiper of VR1 to ground). Here, the output voltage takes half a second to decay due to the 10μF capacitor only being able to discharge through the 51kΩ/10kΩ divider. Of course, any load impedance will cause this to happen much quicker. And it’s doubtful that you’ll be able to wind the potentiometer down any faster than that anyway. Transient response is an important parameter for a regulator since it shows how much it will allow the voltage to vary if the load impedance changes fast. Scope 3 shows how the output voltage shifts with a series of load changes from 250mA to 500mA timebase = sec Scope 3: this scope grab shows a series of load changes from 250mA to 500mA to 750mA to 1A and back to 250mA, with the worst deviation being under 100mV. We made these measurements directly at the output of the PSU. In practice, when using a breadboard, the variation is about three times greater due to the resistance of the breadboard conductors. 29 The underside of the Breadboard PSU. The wires were just for prototyping and aren’t required on the final board, see Fig.2. to 750mA to 1A and back to 250mA. As you can see, the change in output voltage is small, well under 100mA at 1A compared to no load. Scope 4 shows a close-up of the transition from 250mA to 500mA in Scope 3. There are brief spikes of +300/−375mV, but it quickly settles to a steady voltage after about 300μs. Construction The Breadboard PSU is built on a double-sided PCB coded 04112221 that measures 99 x 54mm, as shown in Fig.2. It is available from the PE PCB Service. Apart from the USB socket (CON2) and the current shunts, all the circuit parts can be through-hole types. It could have been smaller if we’d used more surface-­mounting parts, but we would still need to leave room for the potentiometers and heatsinks for the transistors. While this project is useful for beginners, constructors will need reasonable soldering skills as most shunt monitor ICs are only available as SMDs, and quad shunt monitor IC1 has fairly closely-spaced leads. Still, it is not that hard to solder with the right tools, a gentle touch and a bit of patience. We’ve designed the PCB to accept either through-hole or surface mounting capacitors. So, if you have suitable SMD capacitors, you should fit them along with the other surface-mounting parts. While Fig.2 shows SMD capacitors, our photos reveal we built the prototype with through-hole types. Note 30 that SMD ceramics are usually cheaper than equivalent through-hole caps. We’ve extended the pads for the smaller SMD parts to ease assembly. You might get away with simply using a fine-tipped iron, but flux and solder wicking braid will definitely help. Start with IC1, which has the smallest leads of any of the SMDs. Apply flux to its PCB pads and align the part, checking that the pin 1 marking dots on the part and silkscreen line up. Tack one lead, then gently solder the remaining pins if all is still aligned (use a magnifier to check). The solder fillets should form easily if you have the right amount of solder and flux. Use the braid to wick up any excess solder that might form bridges between the pins. timebase = ms Scope 4: a close-up of the 250mA500mA transition in Scope 3. There is a bit of overshoot, but it’s close to being symmetrical. CON2 is a surface-mounting USB socket that locks into place with tabs on its underside. Apply flux and carefully solder the two longer pads for power. After that, solder the larger mechanical tabs on the sides of the USB socket. The two current shunt resistors are on the reverse of the PCB. Align them within their pads and tack one lead. Adjust the position so that the part is squarely within the silkscreen markings. Then solder the other lead and refresh the first lead if necessary. Fit the capacitors now if you are using SMD parts. There are three different values and they are all spread around the PCB. Work with one value at a time to avoid mixing them up. At this point, clean up any excess flux using an appropriate solvent. Be sure to let it dry thoroughly as many such solvents can be flammable. A good strategy for the remaining PCB parts is to work from the lowest profile components up. Start with the resistors, as they are all mounted flat against the PCB. There are 16 of these around the PCB; check the silkscreen values against the resistors before soldering. A multimeter is the most reliable way to check the values as the colour markings can sometimes be ambiguous. Fit the solitary diode D1 next. It is installed near the USB socket and should have its cathode band close to the USB socket. If using through-hole capacitors, fit them next, checking the silkscreen marking against the part marking. Then install the two op amps. Their pin 1 markings should align with the silkscreen and face to the left of the PCB. You could use sockets, although a socket for IC2 might foul the heatsink for Q1; check first before fitting it. It’s generally acceptable to solder them directly to the PCB as you should not need to swap them unless they are faulty, which is unlikely. There are three TO-92 parts; the two smaller transistors, Q2 and Q4, and voltage regulator REG1. Solder them in now, making sure to orient them correctly and don’t get them mixed up. Fit the various headers and jumpers next, but leave CON3 and CON4 to last as they are fitted under the PCB. Check Fig.2 and our photos to see what goes where. Use three-way headers for the two three-way jumpers, JP1 and JP2. Slot them in place, solder one pin and check that the pins are perpendicular to the PCB surface before soldering the remaining pins. Leave the jumper shunts off until testing has been completed. Practical Electronics | December | 2023 The remaining connectors on the top of the PCB (CON5-CON9) are all SIL socket types. It’s even more critical to mount them perpendicular to the PCB as they are designed to plug into a second PCB mounted above. The two larger transistors, Q1 and Q3, need heatsinks. Bend the leads back around 7mm from the body and thread the leads into the PCB holes. Slip the heatsinks in behind the transistors and secure both the transistor and heatsink to the PCB with an 8mm M3 screw on each. A thin layer of thermal paste on the underside of the rabs of the transistor is optional, but will help with heat transfer. Add the washer and tighten the nut firmly to position the transistor and heatsink neatly and squarely. Then you can solder and trim the leads. The remaining larger parts on the top of the PCB should be easy enough; just take care that they are neat. CON1 is adjacent to the CON2 USB socket and the four potentiometers are along one edge of the PCB. You can fit the knobs now. For splined shafts, dial the potentiometers to their midpoints so that the slot is horizontal. Push on the knob so that the indicator points straight up, also at its midpoint. Then wind the knob anti-clockwise to its minimum position, so it is safe for testing. We’ve used red knobs for the current limiting pots (VR3 and VR4) and green knobs (VR1 and VR2) for the voltage setting. Of course there are other colour combinations and you can choose whichever knob colour coding you prefer. Next, fit the tapped spacers now as these form the legs at one end of the Breadboard PSU and will show you how much clearance you have to mount MOD1. MOD1 is mounted to the underside of the PCB near CON1 and CON2. Since it covers the solder pads for some top-side components, ensure you haven’t missed any parts. Trim any leads in that area short, so there is ample clearance. Orient the module according to the VIN and VOUT markings on the PCB. Make sure you check the polarity too, as we have seen some variants of the MT3608 modules that have the connections reversed. Then solder it in place using short lead off-cuts through the pads on both boards. Make sure it doesn’t protrude further than the spacers; otherwise, it will carry the weight at this end of the PCB. Also make sure that the underside of the module is not shorting against Practical Electronics | December | 2023 Fig.2: the Breadboard PSU is meant to be compact, so the PCB is pretty packed with components. CON3 and CON4 are fitted under the PCB to connect directly to a breadboard, while the two current-measuring resistors and boost module MOD1 are also on the underside. CON5-CON9 are mainly for fitting the display module. You can omit MOD1 and CON2 if you only plan to use the DC input at CON1. any leads, then trim the leads that are holding the module. Finally, fit CON3 and CON4. These can be aligned by pushing the header pins into the breadboard’s power rail and then resting the Breadboard PSU PCB in place. We’ve aligned the positive pins with the red markings on the breadboard. Push everything down flat and then solder the ends of the header pins from above. Testing It’s easy to run a few tests to verify everything is in order. You’ll need a multimeter to measure a few different voltages for testing. All are referred to ground; the shell of CON2 (the mini USB socket) or pin 4 of IC2 or IC3 are good places to make this connection. The following three paragraphs assume you have fitted MOD1. If you’ve left it off, skip them. Leave JP1 and JP2 off and connect USB power to CON2. You should see 5V at the right-hand end (USB) of JP2 and the output from the boost module at the right-hand end (BST) of JP1. Adjust the output from the boost module to be 15V or lower. If you know what your maximum working voltage will be, set this around 2V higher. A lower voltage will reduce dissipation in the transistors. If you don’t see the expected voltages, then perform some checks around CON2 and MOD1. Disconnect USB power and apply a suitable supply to CON1. This can be anything from 7V to 15V; CON1 is configured for a positive tip as that arrangement is the most common. The left-hand end of JP1 (JACK) will have a slightly lower voltage than the input at CON1 due to diode D1. If you see nothing there, then the diode or supply might have the wrong polarity. You should measure about 5V on the left-hand end (REG) of JP2. If 31 you don’t, the problem is likely to be with REG1. If all is well, connect your preferred power supply and set JP1 and JP2 to suit. In practice, that means both jumper shunts across the left and centre pins for power at the DC jack, or both jumper shunts across the right and centre pins for USB power. Our photos show the jumpers set up for power being applied at the DC jack, although other combinations may be possible. You should now be able to test the outputs with a multimeter. The leftmost potentiometers adjust CON3, which is next to them. The other potentiometers adjust CON4. Move VR2 and VR4 (the current adjust potentiometers) slightly above their lowest position; otherwise, the output is completely shut off. Then slowly increase VR1 and VR3 and check that the voltage changes. The maximum voltage will be reached well before the clockwise position on the potentiometers and will be around 1V below the voltage selected by JP1. Using it Once it’s plugged into a breadboard, there’s not much more to using the Breadboard PSU. Use the potentiometers to adjust the voltages and current limits as needed. With legs fitted at the end near CON1 and CON2, the Breadboard PSU rests on CON3 and CON4 on a breadboard at the other end. It’s designed to be used more or less in the raw state. If you don’t plan to fit the display, you could use extra tapped spacers to mount a sheet of card or plastic above the exposed components for protection. The transistors operate in linear mode, so they will dissipate quite a bit of power, depending on the settings and supply voltage. If the Breadboard PSU is current limiting into a short circuit, the dissipation will be at its highest. The recommended heatsinks are suitable for up to a few watts, so with a 15V supply, you can set the current limit up to around 200mA without worrying about overheating GET T LATES HE T COP Y OF TEACH OUR -IN SE RIES Order direct from Electron Publishing AVAILA BL NOW! E PRICE £8.99 (includes P&P to UK if ordered direct from us) the transistors. Even at higher dissipation levels, as long as you monitor the current and switch off the supply if it’s drawing more than expected, it should survive brief overloads. For higher supplied currents, especially if you only need much lower voltages, then you should consider a lower input voltage to reduce transistor dissipation. As we mentioned earlier, we have also designed an add-on display module, as shown in the lead photo. It provides readouts of the set and actual currents and voltages. Its operation and construction are shown in detail starting on page 34 of this issue. We think it’s a really handy addition – well worth making. The display module can also estimate transistor dissipation by monitoring the voltages and currents, so it can help avoid situations that could overheat the transistors. Reproduced by arrangement with SILICON CHIP magazine 2023. www.siliconchip.com.au EE FR -ROM CD ELECTRONICS TEACH-IN 9 £8.99 FROM THE PUBLISHERS OF GET TESTING! Electronic test equipment and measuring techniques, plus eight projects to build FREE CD-ROM TWO TEACH -INs FOR THE PRICE OF ONE • Multimeters and a multimeter checker • Oscilloscopes plus a scope calibrator • AC Millivoltmeters with a range extender • Digital measurements plus a logic probe • Frequency measurements and a signal generator • Component measurements plus a semiconductor junction tester PIC n’ Mix Including Practical Digital Signal Processing PLUS... YOUR GUIDE TO THE BBC MICROBIT Teach-In 9 – Get Testing! Teach-In 9 A LOW-COST ARM-BASED SINGLE-BOARD COMPUTER Get Testing Three Microchip PICkit 4 Debugger Guides Files for: PIC n’ Mix PLUS Teach-In 2 -Using PIC Microcontrollers. In PDF format This series of articles provides a broad-based introduction to choosing and using a wide range of test gear, how to get the best out of each item and the pitfalls to avoid. It provides hints and tips on using, and – just as importantly – interpreting the results that you get. The series deals with familiar test gear as well as equipment designed for more specialised applications. The articles have been designed to have the broadest possible appeal and are applicable to all branches of electronics. The series crosses the boundaries of analogue and digital electronics with applications that span the full range of electronics – from a single-stage transistor amplifier to the most sophisticated microcontroller system. There really is something for everyone! Each part includes a simple but useful practical test gear project that will build into a handy gadget that will either extend the features, ranges and usability of an existing item of test equipment or that will serve as a stand-alone instrument. We’ve kept the cost of these projects as low as possible, and most of them can be built for less than £10 (including components, enclosure and circuit board). © 2018 Wimborne Publishing Ltd. www.epemag.com Teach In 9 Cover.indd 1 01/08/2018 19:56 PLUS! You will receive the software for the PIC n’ Mix series of articles and the full Teach-In 2 book – Using PIC Microcontrollers – A practical introduction – in PDF format. Also included are Microchip’s MPLAB ICD 4 In-Circuit Debugger User’s Guide; MPLAB PICkit 4 In-Circuit Debugger Quick Start Guide; and MPLAB PICkit4 Debugger User’s Guide. ORDER YOUR COPY TODAY: www.electronpublishing.com 32 Practical Electronics | December | 2023