Finger Board II assembly instructions.
Construction notes: This kit requires good soldering techniques
due to its small size.
Tools necessary: A fine tip soldering iron and a good wire cutter.
Recommended tools: Mechanical clamp-known as a third hand, fine solder wick to remove excess solder.
Caution: Integrated circuits are static and heat sensitive. Do not apply too much heat with your soldering iron when installing these parts. Please take precautions while handing IC's. To protect against static electricity, ground your body before handling these parts.
|Finger Board parts
Schematic in Acrobat PDF format.
Manual in Acrobat PDF format.
Silkscreen and parts placement layout
Frequently Asked Questions FAQ list.
Start by installing the IC's. Observe proper orientation for pin 1. You may install an IC socket for U7 and U6 but do not socket U5. The installation of a socket for U5 will interfere with U3, the 256kbit ram, which will require the need for a socket. We normally do not install sockets for these IC's.
U5 - 74HC573
U6 - 74HC00
U7 - 74HC138
Install capacitor C6 and the 28 pin IC socket for U3. You may need to snip off the center plastic section of the IC socket so it will fit over U5.
C6 - .1uf monolithic capacitor. The printed value on the capacitor will normally be 104, denoting a .1uf value.
28pin IC socket
Install the 52pin PLCC IC socket for U4. Observe proper orientation for pin 1 before soldering.
Install the resistor R1, R2, R3, R5, R6 and R8. Bend the resistor so that it may stand end up on the PCB.
R1, R2, R5, R6, R8 - 10K ohm
R3 - 1 Meg ohm
Install resistor R4. This is a 47K inline sip resistor. Observe proper orientation for pin 1 before soldering. Pin 1 is usually marked with a dot.
R4 - 47K ohm inline sip resistor. Part#10-1-473
Install capacitor C3 and C4.
C3, C4 - 22pf capacitor (20pf may be substituted)
Install capacitor C1, C2, C3, C5 and C7. Observe the polarity for C1 and C13. Place positive side closest to the silkscreened "+" symbol.
C1 - 1uf tantalum, 25 volts or greater
C2, C5, C7 - .1uf monolithic. The printed value on the capacitor will normally be 104, denoting a .1uf value.
C13 - 10uf tantalum, 6.3 volts or greater
Install diodes D2 and D3. Observe proper orientation. Place the cathode side of the diodes to line up with the silkscreened bar on the PCB.
D2 - 1N4007 or 1N5817
1N5817 has a lower voltage drop while the 1N4007 can handle more current, your choice.
You can omit diode D2 and use solder pad J4 to bridge the connection. We recommend installing D2. This will protect the Finger Board from reverse input supply voltage connections. J4 is located on the bottom side of the board, near JP1.
The following headers are normally installed on the topside of the Finger Board. Depending on user applications all or none of the headers may be soldered in.
Headers are usually purchased in longer lengths and cut down to the size needed. Use headers with a contact lead length of .230"(shorter style).
JP1 - 2 terminal block connector
JP2 - Header 7x2
JP6 - Header 2x2
JP10, JP12, JP13 - installed as one Header 3x2
JP14 - Header 3x2
JP18 - Header 2x1
JP19 - Header 2x1
If you have the one piece Finger Board with attached Communications board, you do not have to install JP14. There are already pcb traces connecting JP14 to JP15.
You can omit JP6 and use the solder pads J1 and J2. By bridging solder pad J1, A/D ref input VRH will be connected to VCC. Bridging solder pad J2 will connect A/D ref input VRL to ground. These two pads are located on the bottom side of the board, near JP6.
The following headers are normally installed on the bottom side of the Finger Board so that prototyping boards can be used. Depending on your actual application, these headers can be placed on top. Trim any excess lead lengths at this time before installing the headers.
JP4 - Header 4x2
JP7 - Header 8x2
JP9 - Header 10x2
JP11, JP8, JP17, JP16 - installed as one Header 12x2
Install reset IC U1 and 5 volt regulator U2. Observe the silkscreened symbols on the PCB for proper placement.
U1 - MC34064 (Motorola)
U2 - LM7805
A low drop-out (LDO) voltage regulator can be substituted for the standard LM7805 regulator. Applications that require low current use such as a solar cell powered Finger Board or running off 4 cell batteries may need a LDO regulator. If you install a LDO regulator, omit diode D2 and bridge solder pad J4. The diode voltage drop will interfere with the LDO lowest voltage regulation. J4 is located on the bottom side of the board, near JP1.
Install crystal Y1. Cut a small piece of Mylar or thin cardboard insulation to prevent a short on the pc board. Punch two small holes for the crystal leads so the insulator can fit against the bottom.
Y1 - 8Mhz crystal
Bridge solder Pad J5 using a small blob of solder. This will connect the SRAM supply to VCC. J5 is located on the bottom side of the board, near JP4.
If you plan to use a standard 256kbit SRAM memory chip and not a Dallas battery backed memory module, do not bridge solder pad J5. See step 22 for optional external SRAM battery backup.
You should wash and clean the completed board before installing U3 and U4. We use water soluble flux solder here at EAS. This permits easy board cleaning. Radio Shack sells flux removing solvent made for pc board cleaning. Take a close look at all solder joints and touch-up any joints that look bad. A 2x or 3x magnifying glass helps to find any solder bridges. When installing the 68HC11 processor, observe pin one polarity. Some PLCC sockets may require firm pressure when pushing in the processor. Also observe proper pin placement when install the memory module.
U4 - MC68HC11A1FN CPU
U3 - DS1230AB/Y Dallas 256kbit (32Kbyte) battery backed static ram. Substitute a DS1244Y if a real time clock is needed. You can also use a Dallas DS1216D 28pin lithium battery socket but will need separate 256kbit 62256-100LP static memory chip.
If you are using a header for JP6, place a couple of jumper shunts on JP6. This is the A/D reference input voltage. Install a shunt across pins 1 and 2 to tie VRH to VCC. Install a shunt across pins 3 and 4 to tie VRL to ground.
A small hole is provided underneath the 68HC11 to be used to remove the processor. Use a small diameter screwdriver to push the processor out of the IC socket.
|Communications Board Assembly
Install U8 on the Communications printed circuit board. Observe proper orientation for pin 1. If you want, you can install a IC socket for U8.
U8 - MAX232CPE (Maxim)
We have noticed when using 3rd party manufactured equivalent Maxim MAX232CPE chips, downloading S19 files from DOS isn't as reliable. Please purchase exact Maxim part for the Communications Board.
Install capacitors C8, C9, C10, C11, C12. Observe the polarity of the capacitors before soldering.
C8, C9, C10, C11, C12 - 1uf tantalum 16 volt or greater.
Install resistor R7 and LED D1. The shorter lead on LED D1 is the cathode. If D1 is installed backwards, the communications board will not operate. Place the cathode side of the LED to line up with the silkscreened bar on the PCB.
R7 - 1K ohm
D1 - HLMP1790 LED
The LED is rated for 2ma. If a higher current model is substituted, the Communications board will not work. You can decide not to install the LED, since it just indicates download mode. The download mode will also be indicated on your computer screen while Interactive C is sending out the pcode.
Tech America (1-800-877-0072) sells a 3ma LED (model#90-1555) that can be substituted for the HLMP-1790. The resistor R7 value must be increased to 2.7K, or else the current drain from the LED will prevent communications
Install switch S1 and S2.
S1, S2 - momentary normally open push button switch.
Use the middle two sets of holes on the PCB when installing the switches.
Install connector P1 and header JP15.
P1 - Female DB9 pin connector
JP15 - Header 3x2
If you have the one piece Finger Board with attached Communications board, you do not have to install JP15. There are already pcb traces connecting JP14 to JP15.
To connect the main CPU board to the Communications board, you will need a short length of ribbon cable and two female IDC connectors (3x2). When making the cable, make sure pin 1 line up together on both connectors. The ribbon cable length should be no more than 1 foot between the CPU board and Communications board. Serial communication errors may occur if cable is too long due to noise. If you need a longer length from your computer to the Finger Board, then increase the length of cable going from the Communications board to the PC serial port, since this length can be as long as 25ft.
When using Interactive C, the Finger Board supports a 16x2 line LCD module connected to header JP2. To connect the LCD module, you will need a short length of ribbon cable and two female IDC connectors (7x2). When making the cable, make sure pin 1 line up together on both connectors. The ribbon cable length should be no more than 1 foot.
If you cannot locate a LCD module, you can purchase one directly from EAS. The cable is included in the price.
The Finger Board II was also designed to allow our LCD module to mount directly on top using a header and socket with the communications board attached.
|Image unavailable at this time.||Optional parts installation
Step 22 SRAM Battery Backup
If you plan to use a standard 256kbit SRAM memory chip and not the Dallas battery backed memory module, install diodes D4 and D5. Place the cathode side of the diodes to line up with the silkscreened bar on the PCB.
Do not bridge solder pad J5.
D4, D5 - 1N5817
Placing a 3 to 5 volt battery on header JP19 will retain the SRAM memory when the main supply voltage is disconnected. We do recommend using the Dallas battery backed memory chip, as it is very reliable. However if you do use standard SRAM memory, use a good quality on/off switch for the power. Power cycle switch bounce can corrupt the data in memory.
|Image unavailable at this time.||Step 23 Remote Serial Reset
To use the remote serial port reset feature, install mosfet Q1 and bridge solder pad J3.
Q1 - BS170 or MOSFET N
If you plan to use Interactive C, do not implement this feature.