Circuit Board Assembly Instructions for Babuinobot 1.0

Transcription

1 Circuit Board Assembly Instructions for Babuinobot 1.0 Brett Nelson January

2 Features Sensor4 input Sensor3 input Sensor2 input 5v power bus Sensor1 input Do not exceed 5v Ground power bus Programming cable header Use FTDI based USB cable with the black wire towards the edge of the board. Reset button Will stop any running program and put chip in programing mode. Motor B power leads Motor A power leads Battery connection Positive lead goes closest to the switch; negative lead is closest to the edge. Supply 7.2-9v power. - - Programming/Run Mode indicator Flashes slowly when in programming mode; flashes quickly when in run mode. Run/Stop button Starts program running when pushed, then stops program if pushed again. Will restart program where it was when last stopped. Piezo speaker On/Off switch Push towards the voltage regulator to switch power on Power On indicator 2

3 Parts Placement 330 Ω resistor 4.7 μf capacitor pushbutton switch 10 kω resistors 01. μf capacitor Atmega168/328 microcontroller 1x6-pin male header 2x6-pin male headers SN H-bridge 01. μf capacitors solder bridges modified 1x4-pin male headers LED 18 pf capacitors 7805CT voltage regulator 16 MHz crystal slide switch - 1x2-pin male header 470 μf 25v capacitor pushbutton switch - 10 kω resistor Piezo speaker LED 330 Ω resistors Jumper Wire: custom length solder bridge 3

4 Electrical Connections This diagram gives an x-ray vision looking down at the top of the board showing the electrical connections with the copper pads underneath. This helps show how all of the components are connected and will be very helpful if you decide to make any changes to the board. Ground Bus Volt Power Bus 4

5 Assembling the Babuinobot 1.0 Circuit Board The following pages will describe step by step the process of building the circuit board. Read the instructions carefully. Check and double check the placement of each component; misplacing a component by even one hole can prevent the board from working and can damage components. Use the close-up pictures and the placement diagrams on pages 2-4 to help place parts correctly. The soldering pads on the board are very close together and it is exceptionally easy to create solder bridges; use only enough solder to fill in the hole and no more. If you are not experienced at soldering, I strongly recommend that you practice before starting this project. Good luck and enjoy! One side of the empty circuit board is tan in color with some thin white lines. This is the side where all of the electrical components will be place, with their leads poking through the holes to the other side. The other side of the board has copper plating. This is the side where the components will be soldered into place. The copper traces provided paths for electricity to go from one component to another. In order for the solder to work well, all pieces must be clean. Wash your hands before beginning to work and avoid touching the copper with your fingers. Before soldering, lightly buff the copper with a plastic scouring pad. Place the 16 pin socket and the 28 pin socket as shown. Make sure the ends with the notches are facing the correct way. If you do not have a 28 pin socket, you can place (2) 14 pin sockets end to end instead(or any combination that gives you 28 pins). notches Place masking tape or electrical tape over the components so that when you flip the board over to solder them, they won't fall out. 5

6 Flip the board over and solder the leads. Usually the tape doesn't hold the components firmly to the board, so I solder one lead on each component, remove the tape, and hold the component firmly to the board with one finger while I briefly remelt the soldered lead. Let go of the component and finish solder the rest of the leads. Apply just enough solder to fill around the hole; adding too much solder will form large blobs that tend to form solder bridges. Clean up any solder bridges with solder braid or a solder sucker. If you use lead based solder, the solder joints should be very shiny and cling to the component lead. I use lead free solder, so the joints that you see in the pictures are not very shiny and don't cling to the component leads as well. Lead solder Lead free solder Place (2) 2x3 dual-row header pins, (1) 1x6 single row header pins, and (2) modified 1x4 single-row header pins as shown. The modified 1x4 headers pins are made by using needle nose pliers to remove the two middle pins from a standard 1x4 single row header. These form the motor lead connections. Insert the short end of the header pins through the circuit board and solder on the other side, leaving the long end of the pins with the black plastic frame above the circuit board. remove Due to a lack of space, there are (4) connections that we are going to make by purposefully creating solder bridges underneath the board. They are shown on the circuit diagram on page 3 as small gray irregular blobs on the H-bridge chip. Add enough solder to bridge the gap separating the pads. These are the ground pins for the H-bridge and will also serve as a heat sink. solder bridges 6

7 Add jumper wires as shown. Again, use tape to hold things in place when you flip the board over to solder. Refer to pages 2-3 if there is any question about where to place components. Use wire cutters to trim the leads after soldering. Add a 0.1 μf capacitor (has 104 stamped on it), (2) 18 pf capacitors, and a 16 MHz crystal as shown. Make sure that the metal lead on the 0.1 uf capacitor does not touch any metal on the orange jumper wire. The insulation on the jumper wires tends to shrink away and expose some of the bare wire when the heat is applied from the soldering iron. Watch for metal-metal contact! Now solder in the reset button, (2) 10 kω resistors (brown-black-orange), and a 330 Ω resistor as shown. Bend the resistor leads as needed. 7

8 Place a 4.7 μf electrolytic capacitor, a 0.1 μf capacitor (has 104 stamped on it), and a small jumper wire on the board and solder in place. Electrolytic capacitors have positive and negative leads and must be place correctly or they will fail and may explode. The black stripe going down the side with a - sign shows the negative lead and in our case must be placed in the outermost hole. The capacitor in the picture on the left is shown sticking out above the board to show where the leads go. Be sure to press it firmly all the way down to the board before soldering it in place. Place the (13) jumper wires as shown. The yellow wire right next to the start/stop pushbutton will need to be bent a little bit to make it fit around the button and should be placed after the button has been soldered. The long yellow jumper with the 90 bend in it will have to be custom formed to fit in place. Place an LED, a 330 Ω resistor (orange-orangebrown), (4) jumper wires, and a 0.1 μf capacitor (has 104 stamped on it) as shown. It's important that the orange jumper wire from the previous step be soldered before placing the green jumper wire so that the leads from the orange wire don't melt the larger insulation on the green wire. smaller LEDs and all other diodes act as one-way valves; they allow electricity to pass through one direction, but will block the flow of electricity if the direction is reversed. If the LED isn't placed right, it will not work. Usually one of the leads is longer than the other and must be connected to the positive source. The shorter lead connects to ground. You can also tell how to hook it up by looking inside the plastic; the negative lead is attached to a much larger piece of metal inside the shorter plastic housing while the positive lead is attached longer to the smaller piece of metal. 8 -

9 Place (2) 330 Ω resistors, (1) 10 kω resistors, and an LED as shown and solder. Watch the polarity on the LED. _ Next, place the slide switch, (2) jumper wires, and 1x2 header pin as shown and solder. The yellow jumper wire will need a slight bend in it. Place the 470 μf capacitor as shown and solder. The negative lead, the one nearest the stripe with the - sign, should go in the hole right next to the 25 that is printed on the board. Be sure to firmly press the capacitor against the board before soldering. 9

10 Place the voltage regulator as shown near the power switch and solder. The leads on the regulator are heavy and there is a built in heatsink, so it will take quite a bit of heat to make everything hot enough to bond with the solder. If you are using an adjustable soldering iron, this would be a good time to turn it up higher. before after notches Insert the SN754410NE H-bridge chip and the Atmega 328/168 Arduino chip into their sockets. If these chips have not been used before, their pins will be splayed out and will not fit into the sockets; carefully place each side of the chip against a flat surface and roll the chip to bend the pins so that they go straight down or have a slight inward bend. Align the notches in the chips as shown> Attach the piezo speaker to the board with double sided tape or hot melt glue. Solder the leads as shown. Check the board over to make sure that everything was placed properly, all leads are soldered, and that there are no solder bridges (except for the four that we purposely made). One way to check for solder bridges is to hold the circuit board up to a bright light and look at the bottom of the board. The light will show through the circuit board except where the copper pads are and the solder; it's pretty easy to see where solder has joined two separate copper pads. Congratulations! You are finished! 10

11 Completed Board (minus the piezo speaker and chips) 11

12 Schematic Diagram 12