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Building our new Super Smooth, Full-range, 10A/230V Speed Controller for Universal Motors Part II – by John Clarke Last month we described the features and circuit details of our new Speed Controller. This month we move on to construction and troubleshooting. T We do not expect that there will be his new Motor Speed Con- is some filing required to remove the troller supersedes the one we two ribs that prevent the bridge mount- any problems with PCBs supplied by the SILICON CHIP OnlineShop or with published in May 2009. We no ing flat against the side of the case. Also decide if you prefer having those supplied in kits. These are of longer recommend that circuit because this new design provides much the feedback control potentiometer high quality and are solder masked, smoother operation and also has much (VR2) mounted on the front lid or screen-printed and shaped with the whether you will use the internal required cutouts. better overload protection. However, if there are any problems, It is constructed on a single PCB trimpot (VR3). repair these as necessary. Similarly, coded 10102141 and measuring 112 if the cut outs in the sides of the PCB x 141mm. It is housed in a diecast Beginning construction First of all, check the PCB for any have not been shaped, they should be metal case measuring 171 x 121 x 55mm. A front panel label measuring etching problems (bridged or broken cut and filed before any components 168 x 118mm is attached to the lid of tracks, etc) and wrongly-drilled holes. are assembled. Check that the PCB fits the case. into the case before startThe PCB includes cuting assembly. outs to match the shape of Following the overlay the case and a cutout for the diagram shown in Fig.9, IEC input connector. This project should only be attempted by constructors with first solder in the resisBefore construction, you extensive experience in mains-powered circuits and with the tors, except the 0.01Ω need to check what bridge knowledge necessary to get it going if something is wrong. resistor, using the colour rectifier is being used for This circuit connects directly to the 230VAC mains and most code table on page 92 BR1. This can be either a components are floating at this voltage. and/or a digital multiPCB mounting type or one meter, to ensure you have that has spade terminals Inadvertent contact with a live circuit could prove lethal. the right resistors in the – the construction varies Do not operate the circuit with mains connected, without the right places. depending on which type case lid being secured with all six screws provided. Always When inserting diode is used. There is no best remove the mains lead from the IEC socket before removing lid. D2 and ZD1 take care choice. Low-voltage trouble-shooting tips are provided later in this with their orientation. For the spade terminal Diode D1 is installed bridge extra wiring is inarticle. later. volved whereas with the But we must reiterate: do not attempt to build this speed We use an IC socket for PCB mounted bridge, there controller if you do not have the experience necessary to do so. This is NOT a project suitable for beginners or the inexperienced! 88  Silicon Chip siliconchip.com.au D1 D1 A G N N 470pF 1 REG1 # 1k 10k 4.7k 1mF +5V 1RV VR1 VR2 0V 2R V V5+ WIPERS SREPIW V0 VR3=Control Alternative to VR2 LMC6482 100nF 1 10k D2 1mF 10k IC2 1mF VR3 PIC16F88 330W 1M LP2950 IC1 2.2k 2.2k 100nF CON10 100mF 1mF 15nF 1M 1W (-) CON7 100nF 10k 220nF 250VAC (X2) – ZD1 4148 100nF 470nF 15V 1W – ~ 100nF ~ ~ + 35A 600V BRIDGE ~ 470W 1W + 1M 1W – 100mF W04 + 10W 1mF 1 + ~ ~ CON5 (WELLWYN OAR3 COVERED WITH 2.5mm VIDAFLEX) IC3 IR2125 470W 1W CON4 – CON7 NOT USED WHEN BR1 MOUNTED ON PCB BR1 0.01W 10nF 250VAC (X2) 220nF 250VAC X2 OUT 100W 1W 100W 1W 100W 1W 100nF 250VAC (X2) CON6 ~ ~ CON4 E C 4.7W EMI FILTER ALL COMPONENTS AND WIRING IN THIS CIRCUIT OPERATE AT MAINS POTENTIAL. DO NOT OPERATE WITH CASE OPEN – ANY CONTACT COULD BE FATAL! Note: # this 100nF capacitor was omitted from the circuit diagram and the parts list published last month Q1 (IGBT) INSULATING WASHER BEHIND CON9 CON8 CON10 Fig.9: all components mount on a single PCB – this overlay diagram will help you get them in the right place and in the right orientation. You should find the same diagram silkA K screened onto the top side of the PCB. A Note that provision is made for a PCBmounting bridge TH1 SL32 10015 rectifier (BR1) or for MAINS IN one which mounts CON1 CON2 CON3 off the board via E N A short spade leads. The alternate wiring diagram (Fig.11, overleaf) shows how to do this. S G Q2 D 2N7000 C 2013 1 4120101 10102141 10A/230V MOTOR SPEED CONTROLLER IC1 only. Be sure to install the IC socket terminals dove-tailed together before diameter Vidaflex heat resistant sleevand the ICs the correct way around being inserted and soldered in place. ing slid over it before inserting into with the notch facing the direction The lead entry side is toward the lower the PCB holes. shown on the overlay. Also, ensure edge of the PCB. VR2/VR3 choices IC2 and IC3 are placed in their correct The 0.01Ω resistor can now be inAs discussed last month, VR2 is position. REG1 and Q2 can now be stalled. It has a 40mm length of 2.5mm optional but gives front-panel control inserted, again taking care to over feedback. Note that if VR2 place each in its correct posiis going to be used, you tion. Q1 is installed later. should include either VR3 Capacitors can be installed • For 230VAC brush (universal) motors or a link in its place on the next, again using the capaci• Extremely smooth and PCB to prevents input AN3 precise motor speed contr tor table. It shows the various ol • from floating. Speed can be controlled codes that are used to indicate from zero to maximum Solder in VR3 or place the capacitance values of the • Superb speed regula tion under load a short wire link (using a MMC, MKT polyester, and • Adjus table speed regulation wi length of resistor lead offth feedback control ceramic capacitors. • Ex ce lle cut) between the central nt low-speed motor opera The electrolytic capacition wiper connection and one tors have their value directly • 2300W (10A) rating of the end pads (either one) marked but must be oriented • Cycle-by-cycle current overload protectio for the VR3 position. n with the correct polarity, as • Ov er-current limiting Next are the spade conshown, as must the small • So ft nectors at CON1-CON3 and sta rtin g diode bridge, BR2, which CON8 & CON9. Spade concan be soldered in now, • NTC Thermistor for initia l surge current limiting nectors are also required at along with the 4-way screw • Fuse protec tion CON4-CON7 if BR1 is a spade terminal. • Rugged case with interf terminal type. erence suppression inc It’s made up of two 2-way Features luded siliconchip.com.au March 2014  89 Install the EMI filter and also the NTC thermistor. The PCB-mounted bridge for BR1 can be mounted now if this is used. This sits as low onto the PCB as possible before being soldered in place. D1 and Q1 are the last components to be soldered to the PCB. Solder them in so their metal flanges are towards the edge of the PCB and their full length leads extending about 1mm below the PCB. Mounting the hardware The front panel artwork can be copied and used as a marking-out template. Note that it does not have a hole position for the main earth bolt, which can be mounted anywhere it doesn’t interfere with anything else. Also shown is a marking-out diagram for the end wall of the case (Fig.12). Jaycar’s MS-4000 EMI filter mounts directly on the PCB and assists greatly in removing switching noise generated by the circuit. Insert the PCB into the case noting that the leads for D1 and Q1 must be kinked outward a little so that the metal flange of each device is parallel to and in contact with the side of the case. Mark the mounting hole positions for diode D1, IGBT Q1 and bridge rectifier, BR1. For the quick connector terminal bridge rectifier type, this is mounted side on against the case side. Holes required for mounting Q1 The IEC connector mounts with about 4mm gap from the base of the case to the bottom of the IEC connector. The hole is made by drilling a series of small holes around the perimeter of the desired shape, knocking out the piece and filing to shape. The earth screw hole is 4mm in diameter. If you are using the PCB-mounted bridge rectifier, file away the two ribs on the side of the case that prevent the bridge mounting flat. INSULATING PAD M3 NUT Q1 (IGBT) & DIODE D1 ALL 6.8mm INSULATED FEMALE QUICK CONNECTORS ALSO HAVE HEATSHRINK SLEEVING K CON8 CON9 G C E N N TH1 SL32 10015 CON1 E A E CON2 N CON3 ~ EMI FILTER A – ~ ~ + BR1 ~ – ~ NYLON CABLE TIES 4148 + ~ N + 10A FUSED IEC PANEL MALE SKT CASE EARTH VIA M4 x 10mm SCREW, EYELET, LOCKWASHER & NUT Q1 (IGBT) INSULATING WASHER BEHIND A A M3 x 15mm SCREW PCB Fig.10: the external wiring to the PCB. Inset top right is the mounting arrangement for D1 and Q1 – an insulating washer is essential between the case and the semiconductors but no insulating bush is needed. D1 CASE CON10 (-) +5V 1RV VR1 VR2 0V 2R V V5+ WIPERS SREPIW V0 VR3=Control Alternative to VR2 C 2013 1 4120101 10102141 10A/230V MOTOR SPEED CONTROLLER ALL COMPONENTS AND WIRING IN THIS CIRCUIT OPERATE AT MAINS POTENTIAL. DO NOT OPERATE WITH CASE OPEN – ANY CONTACT COULD BE FATAL! A E LID EARTH VIA M4 x 10mm SCREW, EYELET, LOCKWASHER & NUT N VR1 GPO 90  Silicon Chip VR2 SPEED FEEDBACK siliconchip.com.au and D1 are 3mm, while a 4mm hole is required for the bridge rectifier. Holes are also required in the lid for VR1 and VR2 (if required) and the earth terminal, with a cutout and holes for the mains general purpose outlet (GPO). There are locating spigots on both VR1 and VR2 which prevent the potentiometer body from rotating when the knob is turned. The holes for these (so the spigot will be captive in the hole.) do not need to be drilled fully through to the front of the lid panel. All holes should be de-burred on the inside of the case with a countersinking tool or larger drill to round off the sharp edges. For D1 and Q1, the edges must be rounded to prevent punch-through of the insulating washers. Attach the PCB to the case with the two supplied screws with the case plus an extra two M3.5 x 6mm screws. Secure D1 and Q1 to the case with a screw, nut and silicone insulating washer. No insulating bushes are necessary as the packaging of D1 and Q1 have insulation between the mounting screw hole and metal face. The arrangement for this is shown in the inset in Fig.10. After mounting D1 and Q1, check that the metal tabs of the devices are isolated from the case by measuring the resistance with a multimeter. The meter should show CON1 CON2 E N a very high resistance measurement between the case and any of the diode and IGBT leads. The complete wiring diagram is shown in Fig.10. The earthing details of the case are most important since the IGBT, D1 and the potentiometers, VR1 and VR2 are all at 230VAC mains potential yet are attached to the case. If the insulating washers or the insulation of a potentiometer were to break down, the case would be live (ie, at 230VAC) if it was not properly earthed. For the same reason, the case lid must also be independently earthed. The bridge rectifier (BR1) is secured to the case with an M4 screw and nut. CON3 ~ EMI FILTER CON6 + A Here’s a close-up of the mounting for the IGBT (Q1) with its insulation washer underneath. Diode D1 is similarly mounted. The cambric insulation at top right covers the 0.01Ω resistor – ~ + + ~ ~ CON4 OUT ~ ~ CON5 – 4148 1 CON10 (-) CON7 +5V 1RV VR1 VR2 0V 2R V V5+ WIPERS SREPIW V0 VR3=Control Alternative to VR2 NYLON CABLE TIES 1 C 2013 1 4120101 10102141 10A/230V MOTOR SPEED CONTROLLER BR1 – ~ ~ OFF-BOARD BRIDGE RECTIFIER CONNECTED TO PCB VIA FOUR LENGTHS OF 10A/230V WIRE, WITH 6.8mm INSULATED FEMALE QUICK CONNECTORS AT EACH END, PLUS HEATSHRINK SLEEVES + Fig. 11: if your bridge rectifier (BR1) is designed for off-the-PCB mounting, here’s how to wire it. You’ll need to make up some short spade-lug leads. siliconchip.com.au It does not require an insulating washer between its body and the case. Cut the potentiometer shafts to length to suit the knobs. Then install the potentiometers. These are mounted with up to two washers between the pot and the lid for the locating spigot to fit neatly into its locating hole. Fit knobs to the shafts. The central pointer on each knob may require prising out and relocating to the correct orientation. All mains wiring must be done using 10A 250VAC rated wire. Wiring for the potentiometer must also be mains rated but it does not need to be 10A rated. The IEC connector must be wired using the correct wire colours (brown for Active, blue for Neutral and green/yellow striped wire for Earth). Use quick connectors for the mains wiring connection to the PCB connectors. Wires to the IEC connector need to be insulated with heatshrink tubing covering all exposed metal terminals for the Active and Neutral wiring. For earthing, solder two earth wires from the IEC connector. Each wire should loop through the hole in the earth terminal and be wrapped back on itself so the wire is essentially captured before soldering to the terminal. Make sure the earth terminal is heated sufficiently with the soldering iron so the solder wets and adheres properly to both terminal and wire. One end of the earth wire is crimped to the earth eyelet and the other to the GPO earth terminal and the earth eyelet on the lid. It is important to use one continuous earth wire length with just the insulation stripped back in the middle to terminate into the GPO earth screw terminal. The earth eyelets are secured with M4 screws, a star washer and nut, with March 2014  91 place using cable ties as shown. This minimises the possibility of any wire breaking loose and making contact with the case. Testing The view inside the completed project. Note that there is no power lead connected to the IEC socket in this picture – the case should never be open with power applied! a second nut used as a locknut. Note that a countersunk screw is used on the lid. The IEC connector is secured with the M3 x 10mm countersunk screws, star washers and nuts. Similarly, the GPO is secured with M4 screws, star washers and nuts. Wire up the potentiometer, again Capacitor Codes Value μF IEC EIA value code code 470nF 0.47μF 470n 474 100nF 0.1μF 100n 104 15nF .015μF 15n 153 10nF .01μF 10n 103 1nF .001μF 1n0 102 470pF NA 470p 471 All “X2” class will have printed values 92  Silicon Chip using 250VAC-rated wire. The reason for this voltage rating this is to ensure that there is no insulation breakdown to case. Finally, hold the wiring in Before you power up the circuit, check all of your wiring very carefully against the overlay and wiring diagram. Also check that the case and lid are connected to the earth pin of the power socket. If you are satisfied that all is correct, you are almost ready to screw the lid onto the case. Set VR1 and VR2 fully anticlockwise. If you are not using VR2, set VR3 anticlockwise instead. When screwing the lid on, note that the case is supplied with a rubber seal that goes around a channel in the lid. Do not be tempted to operate the speed controller without the lid in place and screwed in position. Any delving into the circuitry when it power is connected is potentially lethal. Preferably, use an earth leakage circuit breaker (safety switch) on the mains supply. If there isn’t one already installed in your fuse box, use an in-line type. The easiest way to test the circuit operation is to connect a load such as a standard (ie, non-speed-controlled) electric drill. Apply power and check that you can vary the drill speed with VR1. Some motors may require adjustment of VR2 for best speed regulation. If using VR3 instead this must be done on a trial-and-error basis with the power off. Disconnect power to the controller by unplugging the IEC mains power lead from the mains wall outlet, adjust VR3 very slightly and replace the lid. In practice, if VR2 or VR3 is adjusted too far clockwise, the motor may tend to be overcompensated when loaded Resistor Colour Codes p p p p p p p p p p No. 3 3 1 2 1 2 1 3 1 1 Value 1MΩ 10kΩ 4.7kΩ 2.2kΩ 1kΩ 470Ω 330Ω 100Ω 10Ω 4.7Ω 4-Band Code(1%) 5-Band Code (1%) brown black green brown brown black black yellow brown brown black orange brown brown black black red brown yellow violet red brown yellow violet black brown brown red red red brown red red black brown brown brown black red brown brown black black brown brown yellow violet brown brown yellow violet black black brown orange orange brown brown orange orange black black brown brown black brown brown brown black black black brown brown black black brown brown black black gold brown yellow violet black gold (5%) n/a siliconchip.com.au includes any exposed metal parts on components except those that are tied to the earthed chassis of the case. Do not touch any part of the circuit when it is plugged into a mains outlet. Always remove the plug from the mains outlet before touching or working on any part of the circuit. Before going any further, check the fuse, then give your PCB another thorough check (using a magnifying glass?). Check for incorrectly placed components and for component orientation. Also check solder joints. Fortunately, there is a safe way to check most of the circuit and that is to operate it from a low voltage (12-14V with at least a 20mA current capability) DC supply. The end of the diecast case must be drilled and filed to house the fused IEC mains input socket along with a countersunk 4mm hole for the main earth bolt (see diagram below). and will actually speed up. It may even hunt back and forth between a fast and slow speed. If this happens, readjust VR2 or VR3 anticlockwise for best results. If you are using a drill at fairly low speed, the motor should not slow down by much as you put a reasonable load on it. Note that the feedback feature where the idle current can be dialled out will prevent the motor speed from increasing with increasing feedback control adjustment. The idle current can be dialled out by running the motor at the desired speed and then rotating VR2 anticlockwise so that the controller measures the idle current. Then readjust VR2 clockwise to its required position for best control. The motor speed is then only controlled for current that exceeds the idle current. This feature cannot be easily activated using VR3. This speed controller must NOT be used with appliances that already have a continuously variable speed controller built into the trigger. You can use the speed controller with electric drills that have two-speed gearbox switching (ie, non-electronic) speed control. One final point; if you are using this controller with a high power tool such as a large circular saw or 2HP router, it will not give the same kick when starting. That is because of the soft start – the motor will take slightly longer to come up to full speed. This is due to both the NTC thermistor and PWM soft start by the micro. Troubleshooting C L If the speed controller does not work when you apply power, it’s time to do some troubleshooting. First, a reminder: all of the circuitry is at 230VAC mains potential and can be lethal. This Earth 4mm 3mm IEC mains connector cutout Case End View Tools with “Soft Start” Circuits When testing the 230V 10A Brush Motor Speed Controller on a 220-240VAC 6.5A Makita LS1017L Sliding Compound Saw, the motor would not operate at all. A quick search on the ’net revealed that this saw includes a soft start circuit to prevent the otherwise massive surge current at start up. Presumably, the soft start circuit requires an AC supply in order to work. The full wave rectified DC voltage from the Motor Speed Controller prevents it working. The accompanying photograph shows the soft start module. This is located just inside the end cap of the motor where it receives cooling air drawn in through the motor fan. The C terminal connects to mains Active via the trigger on switch for the saw. The A terminal connects to mains Neutral. The soft start connection is between terminals A and B. By disconnecting the soft start A & B terminals then bridging the spade lugs which originally connected to them, we were able to use the Motor Speed Controller with this saw. 3mm Fig12: drilling detail for the end of the case shown above. Photocopy this and stick it to the end of the case, then drill right through it. siliconchip.com.au March 2014  93 Suitable for brush (universal) motors up to 10A 230VAC Do Not Use with induction or shaded-pole motors Speed GPO CUTOUT . . . SILICON CHIP Full Range Speed Controller for 230V Brush Motors . . . Set idle current . .. . . + . . . . . . .. . . + . . . . . Feedback Fig.13: this same-size front panel label can also be used as a drilling/cutting template as well as the final label – if you want it in colour, it can be downloaded from siliconchip.com.au and printed on a colour printer. The 4mm countersunk hole for the lid earth screw is not shown – it can go anywhere it doesn’t interfere with controls, etc. When applied, the label hides its location. Remember that most plugpacks supply significantly above their rated voltage when unloaded so we would always err on the lower side, ie, 12V rather than 14V. You must have the 230VAC mains disconnected from the controller by unplugging the IEC mains lead from the controller and the mains socket. The supply is connected to zener diode ZD1 with the positive connecting to the cathode (striped end) and the negative connecting to the anode. Before you connect the supply, measure it to make sure it is not exceeding 14V, otherwise you may damage the 15V zener diode. A multimeter can be used to test voltages with the negative lead to the negative supply (anode of ZD1). Firstly, check that there is supply at both pin 1 & 8 of IC3, This voltage should be the same as your power supply connection. Pin 14 of IC1 should be about 5V (4.85 to 5.15V) as should pin 8 of IC2. Voltage on the wipers of VR1 and VR2 should be adjustable from 0V to 5V when rotating the potentiometer to 94  Silicon Chip its full extremes. Pin 6 of IC2b should be 3.4V. Pin 9 of IC1 should be adjustable from 0V to 5V as VR1 is adjusted over its full range. This is a DC measurement of the PWM signal. Pin 7 of IC3 should range from 0V through to the power supply voltage with VR1 adjustment. A similar voltage range will be available on the gate of Q1. If the gate voltage remains at 0V, then suspect a damaged IGBT or a short from gate to ground. If your meter can read frequency, the PWM signal at pin 9 of IC1 should give a reading of 980Hz when VR1 is around mid setting. You will not get a frequency measurement with VR1 set at either extreme end of its rotation. Measuring the resistance between IGBT pins is a simple way to check this component. If there is a short circuit between collector and emitter, or if the gate is shorted to the emitter, then the IGBT is likely faulty unless there is a short on the PCB instead. Diode (D1) operation can be checked using the diode test on your multimeter - there should not be a short circuit between anode and cathode. Be sure to remove the power supply connection and replace the lid before reconnecting to the mains. If the live circuit must be worked on, it must be operated via a 1:1 mains isolation transformer and having an earth leakage circuit breaker (safety switch) installed. Incidentally, do not try to monitor the waveforms with an oscilloscope when powered from the mains unless you know exactly what you are doing. Ideally it needs with a scope with true differential inputs or a mains isolation transformer. And a final warning! The entire circuit of this motor speed controller floats at 230VAC. It is potentially lethal. Do not build it unless you know exactly what you are doing. Do not touch any part of the circuit while power is applied from the mains and do not operate the circuit outside its metal case or with its lid off. This circuit is not suitable for induction motors or shaded pole motors such as those used in fans. SC siliconchip.com.au