Technical Section - Constructing the Motor Controllers
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Constructing The Motor Controllers Identifying Components Identify all your components and lay them out over the diagrams to ensure you have them all. Hint: Print out a copy of the figure below to help you identify parts.
As a general rule it is easier to solder in components with a low profile first, such as wire links and resistors, and finish with soldering the high profile components such as the capacitors. Component Insertion 1 – Large Resistors, Wire Links and Test Point Hint: The board will look more professional if the resistors are all the same way round. 1. Large Resistors. · Take the larger 1K and 10R resistors and bend both resistor wires by hand through 90 degrees close to the body of the resistor. · Insert the resistors in the holes shown below so that they lie flat on the board. · Cut off the excess wire 3mm from the under surface and solder them in. Keep the wire offcuts as they will be used later as wire links and a test point. 2. Wire Links. · Bend the ends of the two wire links over with a pair of long nose pliers at the length required. · Insert the two wire links in the correct holes of the Printed Circuit Board (PCB) so that they lie flat on the top surface of the board. · Hold them close and flat to the board with some masking tape. · Cut off the excess wire 3mm from the under surface and solder them in. · Remove the masking tape. 3. Negative Test Point: · Bend the third wire round the ends of the long nose pliers and insert the loop into the two holes in the wide earth track. The loop should stick up about 3mm for you to clip a test lead to it. Hint: Solder one end of the loop first. Adjust the height of the loop and then solder in the other end
Component Insertion 2 – Small Resistors 1. Check the Values of the small resistors from the colour code and bend both resistor wires using pointed nose pliers through 90 degrees so that the bent leads are the same distance apart as the holes. 2. Insert the resistors, cut off the excess wire 3mm from the under surface and solder them in. Hint: You can hold small components like these close to the board with masking tape while you solder them into the board.
Component Insertion 3 - Diodes Hint: Note the two different types, size and numbers. 1. Bend the wires using pointed nosed pliers through 90 degrees so that the bent leads are the same distance apart as the holes. 2. Insert the Diodes with the CORRECT ORIENTATION. The white band denotes the negative end. 3. Cut off the excess wire 3mm from the under surface and solder them in.
Component Insertion 4 – Radio Control Leads 1. Insert the radio control wires through the restraint holes from the under side of the board (Black wire to the edge of the board). Hint: Squeeze the three coloured wires together so that they will fit through the circular hole and push them through about 4 cm so that you can bend over the wire and line the wires up straight with the holes. Note, It is not easy to get all three wires inserted in these holes. 2. Solder in the wires with the CORRECT ORIENTATION (Black to the edge of board).
Component Insertion 5 – IC Sockets, Opto-Isolator and Voltage Regulators 1. IC Sockets. Insert and solder in the two sockets for the ICs with the small indentation towards the top of the board. The socket must lie flat on the board. Note: Check that all the contacts are fully down with none sticking up above the plastic. Hint: Solder two opposite corner pins first and then ensure the socket is flush with the board before soldering the rest of the pins. 2. Opto Isolator. Insert and solder in the Opto-Isolator with the CORRECT ORIENTATION for pin No 1 (Line to the left side of the board). 3. Voltage Regulators. Insert and solder the 5v and 12v voltage regulators in the CORRECT POSITIONS with the CORRECT ORIENTATION.
Component Insertion 6 – LED, Resonator, Plugs and Jumper 1. LED. Insert and solder in the Light Emitting Diode (LED) with the CORRECT ORIENTATION. The longer lead and flat edge is the red side (R). 2. Resonator. Insert and solder in the resonator (Either way round) 3. Plugs and Jumper. · Insert and solder in the white Output Plug (three pins) · Insert and solder in the three black Jumper Plugs (three pins) with the shorter pins through the PCB · Insert and solder in the white external LED Plug (two pins) with the tab towards the edge of the board. · Fit the red Jumper to the two top pins as shown.
Component Inertion 7 – Capacitors 1. Insert
and solder the four 0.22uF small capacitors. 0.22uF = 224 2. Insert and solder the large capacitors noting their different values and CORRECT ORIENTATION. Note: The white stripe denotes the negative connection of electrolytic capacitors
Component Insertion 8 – Connecting Wires 1. Twist and tin the ends of the wires, but do not use too much solder or the wires will not go through the holes, ensuring that no strands of copper wire are left on top of the board Hint: The big copper areas will take longer to heat up 2. Insert the red and black heavy wire connections through the restraint holes and solder to the lower surface (lots of heat required). The red wire is soldered to the copper labelled POS 3. Insert the two grey heavy wire motor connections through the restraint holes and solder to the lower surface (MOTOR). 4. Finally, pull these four wires back through the restraint holes whilst pressing the wire flat against the top surface of the board. 5. Attach (by crimping) red and blue Male Spade terminals to the longer red and black power wires. 6. Attach (by crimping) red and blue Female Spade terminals to the grey motor wires. Note: The colour of the connectors on the grey wires is not important. (We put the red connector on the wire attached to the centre of the board).
Component Insertion 9 – MOSFETS and Insulation Spacer 1. Insert the four MOSFETS in the PCB and ensure the MOSFET holes line up with the holes in the PCB. DO NOT SOLDER THE MOSFET LEGS UNTIL THE HEAT SINK IS BOLTED DOWN. Note: The MOSFET legs are supplied pre bent through 90 degrees away from their flat side. 2.
1. Check the top and bottom of the heat sink is free of burrs and the holes are clear. The under surface must be smooth to the touch as rough edges and burrs will cut through the insulation sheet and cause an expensive short circuit.
2. Insert the four black top hats in the top of the heat sink. 3. Fit the green Insulation sheet onto the underside of the heat sink and ensure the four black top hats poke through the holes in the insulation sheet. 4. Insert the bolts from the underside of the PCB and carefully place the heat sink on top of the MOSFETS. The assembly should be in the following order from bottom to top: 2.5mm bolt – PCB – Insulating spacer – MOSFET – Insulating sheet – Heat sink plate - Black plastic top hat – Nut on top.
Hint: Take great care fitting the heat sink as if you try to force the black top hats into the holes you may squash them and end up with blown MOSFETs caused by an electrical short circuit. 5. Initially fit all four of the nuts FINGER TIGHT on top. Ensure the black plastic top hats are still located in the MOSFET tabs and the top hats are flush with the top of the heatsink. This is very important to ensure the screws are insulated from the MOSFETS. Hint: You may need to remove the black top hat and align the MOSFET and holes with a small screwdriver in order to get the top hats to sit flush with the heat sink. 6. When all the top hats are correctly seated, tighten the nuts fully ensuring that the MOSFETS are sandwiched flat without touching each other. 7. Cut off half the length of the MOSFET pins protruding through the PCB and bend over the Drain and Source pins under the board towards the large area of copper (see picture below). Hint: If you wish, you may carefully scrape away the green insulation film over the copper to allow you to solder the pins along their full length. This will ensure there is a good high current connection between the MOSFET pins and the large areas of copper. (This is not strictly necessary unless you plan to fit larger motors which could draw very high currents). 8. Solder all the pins and then cut off the excess length of the Gate pin. Note: The only components not fitted prior to testing are the two ICs. Fit a small cable tie wrap round the four wires near the edge of the board
The Completed Board – Top View
The Completed Board – Bottom View Configuring The Boards as Master and Slave Two motor drive boards are required to run your robot. They are made as identical boards and configured as a Master Board or a Slave Board by the position of a jumper. Connecting the top two jumper pins together configures the board as a Master and connecting the bottom two jumper pins together configures the board as a Slave. Note: The other two sets of jumper pins are for changing the characteristics of the Rampaging Chariot control laws.
· For the Master board both radio control leads are used and these plug into Channel 2 and Channel 4 of the radio receiver. · For the Slave board the Channel 4 lead is not used and should be coiled up and insulated. The Channel 2 lead should be extended with the extension wire provided and plugged into the Output plug on the Master board (Black wire towards the edge of the board). Making the Test Equipment Connect up the test equipment parts as shown. If there is a major fault the bulb will light and protect the MOSFETS. If this happens, disconnect power immediately as the bulb and resistor will get extremely hot quite quickly and will burn you.
12v Halogen Bulb and 6R8 10W Resistor For Initial Testing of Small Motor
Small 3 volt Motor with 47R Series Resister Next The next section is on the testing of the motor controller boards |
