AVR Scope Clock Assembly

 

 

Assembly Instructions of the Dutchtronix AVR Oscilloscope Clock, Hardware 3.1, Enhanced kit

Please use the pictures and parts list below as a reference. Most of the components can be easily identified and they are clearly marked on the PCB.  Here is some extra information:

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The five 10K resistors R1-R5 have color codes Brown Black Orange

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The three 1K resistors R6-R7 and R14 have color codes Brown Black Red

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The 470R resistor R9 has color codes Yellow Violet Brown

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The 4K7 resistor R13 has color code Yellow Violet Red

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The red LED D1 and green LED D2 has 2 uneven legs. The longer leg is the +, the shorter one the -. The positive side (+) of these LEDs are clearly marked on the PCB.

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The BAT-42 diodes D3-D4 come on a strip.

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There is 1 transistor, a 2N3904. Bent the base leg of this transistor towards the curved part of the transistor body and straighten the other 2 legs.  Now you have the transistor triangle which can be inserted in the board.

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The ATmega328p is pre-programmed with both the boot loader and the Clock firmware.

Pay attention to:

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The terminals CH1 and CH2 are easiest installed when done as the first item on the PCB; solder them on the bottom side.

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Install the IC sockets next. Solder just 2 pins on opposite ends of each socket first and make sure the socket is properly seated before soldering the other pins.

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Capacitor C1-C2, C5, C12-C16, C18, C3-C4 are ceramic, non-polarized capacitors. The Electrolytic Capacitors C6-C8 and C17 are polarized.

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The front of the Backup battery (lettering) is the + side. The battery legs will need to be squeezed a little to fit in the holes; be careful doing this so the legs don't break. Please bend the unused tabs on the battery away to reduce any risk of shorting the battery. The positive (+) side of the battery is clearly marked on the PCB.

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Do not insert any components in the vias, which are small holes to transfer a signal from one side of the board to the other side.

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Install the Power (2-pin) polarized header with the flat back towards the center of the board in the location marked "VCCPOWER".

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Install the RS-232 (3-pin) polarized header with the flat back towards the center of the board in the location marked "RS232".

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All ICs are oriented (pin 1) towards the left of the PCB.

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Install a 2 pin header in the location marked "1PPS" and then put one of the supplied shunts on the 2 pins.

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Install a 3 pin header in the location marked "VCCSELECT" and then put a shunt on the 2 pins closest to the "VCCPOWER" polarized header.

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Install 3 pin headers in the locations marked "TXROUTE" and "RXROUTE", then put a shunt on the right most pins of each of these headers (next to the 3 pin RS232 header)

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If installing IC6 (the FT232RL USB chip, not included), do this as early as possible, but certainly before installing the optional 10-pin ISP header.

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The optional 10-pin ISP header is only useful if you intend to program the AVR microcontroller directly and have the appropriate programmer available. This header is not included.

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Resistor R7 is marked incorrectly as 2K. This should be 1K and this is the value supplied in the kit.

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Trimpot R8 is marked incorrectly as 2K. This should be 1K and this is the value supplied in the kit

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Install the large connectors last; this includes the 2 BNC connectors and the DB9 connector.

The following components are unpopulated in the "Enhanced" kit:

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IC6, C9, C10, C11, L1, X2: these are the USB interface components

 

Cable Connection:

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The easiest method to power the AVR Oscilloscope clock is to use an external wall wart, voltage range 7-15V, with a 5.5 mm (external diameter) center positive DC connector. The proper plug is included with the kit and you can replace the plug on your wall wart if that one doesn't fit.

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The AVR Oscilloscope Clock kit can also be powered  by an external 5V regulated power source.

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The on-board RS-232 level Serial Port is completely optional but can be used for:

 

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Control the clock using a command line interface (for example send NTP time to the clock)

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Run the terminal display application

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Connect the clock to a GPS device

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Upgrade the clock firmware

 

The onboard female DB-9 connector allows the use of a standard Serial Cable. Such a cable has one female DB-9 connector and one male DB-9 connector. The male DB-9 connector plugs into the female DB-9 connector on the clock. These cables also connect the proper RX and TX pins on each side of the cable (crossover cable.)

However, a 3-pin polarized header is also available for use with a custom cable, similar to the original Dutchtronix AVR Oscilloscope Clock Hardware 2-0. The clock side connector needed to make a cable to connect to the RS-232 serial 3-pin polarized header is included with the kit. These parts consist of 3 crimp connectors and 1 terminal housings. To make the AVR clock side of this serial cable, you need to attach three crimp pins to the three serial cable wires. A special crimping tool is preferred but you can also use pliers and use a tiny bit of solder to make sure the connection is secure. Once the crimp pins are attached, you just slide them into the 3 position terminal housing. Make sure you line up the pins correctly:

 

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3-pin connector - 1:GND,  2:out/RXpc, 3:in/TXpc.

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DB-9 connector  - 5:GND,  2:RX,       3:TX.

 

Pin 1 on the RS232 3-pin polarized header is the right-most pin. It is marked on the PCB but invisible once you install the header. Your connector must match this.

Note that the crimp pins have a little tab on them. This tab fits perfectly in a small opening in the terminal housing; you'll hear it click if it is in the proper position. You can remove a crimp pin from the terminal housing by pushing in this tab using a very small screwdriver through the small opening, while pulling the wire.

 

Here are some links on how to make these kind of connectors:

 

        http://www.societyofrobots.com/electronics_wire_connector.shtml

        http://www.hansenhobbies.com/products/connectors/Connectors.pdf

 

Other instructions:

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Install components in order of increased height. For example do the probe connectors first, followed by the IC sockets,  the resistors and the diodes. This way, you can lay the board face down while soldering the bottom side.

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It is advised to use some glue when installing the BNC connectors. This will secure them to the PCB and will prevent excessive force on the connection wires. Apply the glue towards the edge of the PCB so it doesn't interfere with the connection wires, which need to be soldered to the PCB.

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Do not install the 4 ICs initially. When complete, before applying power, test the voltage at the right side junction of diodes D3 and D4. It should read about 3V from the backup battery. Next apply power and test the IC power supply points (IC1 pin 7, IC2 pin 15, IC3 pin 8, IC4 pin 16). If that all tests OK, install the ICs (all are oriented (pin 1) to the left)

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After the first power up, the RTC may report a low battery status. This usually goes away after a couple of power cycles. It can also be cleared by writing the correct time to the clock (long push on the S1 push button switch enters Time Set mode) followed by a clock reset. See the FAQ for more details.

 

Pictures of the assembled board:

 

 

 

 

 
       

 

 

Parts List Dutchtronix AVR Oscilloscope Clock

hardware 3.1 Enhanced kit

 

Printed Circuit Board

 

1

PCB

ATmega328p-20PU Microcontroller

IC1

1

Preprogrammed CPU

AD7302 D/A Converter

IC2

1

Creates Voltage levels

NXP/Philips RTC PCF8563

IC3

1

RTC

LM7805

IC4

1

Power Supply regulator

HIN232ACP Level Converter IC5 1 RS-232

Lithium battery

BATTERY

1

Keep time when turned off

22 pF caps

C3-C4

2

For Atmega Crystal

100 nF cap

C1-C2,C5,
C12-C16,C18

9

Power stability, DC-DC

10 uF cap

C7-C8

2

Power stability

100 uF cap

C6,C17

2

Power stability

10K pull-up resistors

R1-R5

5

Glue

1K resistor

R6-R7,R14

3

Glue

470R Resistor

R9

1

LED current limiter

4K7 Resistor

R13

1

Intensity Inverter

1K Trimpot

R8

1

Reference Voltage

3 mm red led

D1

1

Power indicator

3 mm green led

D2

1

User Interface

BAT-42 schottky diodes

D3-D4

2

Battery Protection

1N4001 diode

D5

1

Reverse polarity protection

28 pin socket

IC1 socket

1

CPU

20 pin socket

IC2 socket

1

DAC

8 pin socket

IC3 socket

1

RTC

16 pin socket

IC4 socket

1

RS232

20 Mhz crystal

Q1

1

CPU Crystal

2N3904 NPN

Q3

1

Intensity Inverter

32Khz crystal

Q4

1

for RTC

Momentary Tactile switch

S1-S2

2

User Interface

Power Switch

S3

1

Power

Power Jack

J1

1

Power

2-pin header

POWER-M

1

Power

BNC connectors

J2-J3

2

Scope Connectors

Turret Terminals

CH1-CH2

2

Scope connectors

shunt for headers

SHORT

4

Various

2-pin header

JP6

1

INT0 feed

3-pin header

GND

1

Ground for probes

1-pin header

Z

1

Intensity Control

1-pin header

ZINV

1

Intensity Control

3-pin header

VCCSELECT

1

Power source Selection

3-pin header

RXROUTE

1

RS232

3-pin header

TXROUTE

1

RS232

3-pin RS-232 connector header

RS-232-M

1

RS232

3-pin RS-232 connector socket

RS-232-F

1

RS232

Crimp Pins

 

3

RS232

DB-9 connector X1 1 RS232

 

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