> INFILTEC: Model QM-1.0 Long-Period Seismometer Electronics Kit Infiltec big logo

Building a QM-1.0-3704-Kit.

Detailed information on building Infiltec
electronics for a long-period seismometer.

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INTRODUCTION:
Welcome to The Inexpensive Seismometer Project, an attempt reduce the cost and complexity of amateur seismic systems.

This page is about my project to build simpler and less expensive amateur long-period seismometers by using microprocessors and other new chips, such as switched capacitor filters. Long-period seismometers are useful for detecting and analyzing distant teleseismic activity (worldwide). For more general information on other types of seismometers and links to web resources, see my main seismometer page. Click here for information on my short period system.
PICTURES OF QM-1.0 SYSTEM:

(Click on thumbnails below for full screen images)
QM-1.0-3074 Exterior.

QM-1.0-3074 Interior.

QM-1.0-3074 circuit board, enclosure, pickup coil and magnet.
QM-1.0 Long Period Seismometer Electronics Kit Specifications:
- Amplification is single stage, low noise, 1100x voltage.
- Amplifier chip: AD8628 auto-zero, low-noise, precision, rail-to-rail output.
- Low-pass filter is an 8 pole bessel filter set by capacitor to a 1 Hz cutoff.
- Filter chip: MAX7401CPA 8th order, low-pass, Bessel, switched capacitor filter.
- A to D: 1 channel onboard microprocessor, 16 bits covering a 0-5 volt range.
- Microprocessor: 8 bit, 4 mHz PIC14000 OTP with onboard 16 bit A/D and serial I/O.
- Microprocessor software: burned into PIC14000, controls A to D, time integration, etc.
- Microprocessor software tracks long term (minutes) changes in mean due to temperature changes.
- Power required: 2 ma @ 5 volts, available from serial port.
- Voltage regulator chip: micropower precision LP2950ACZ-5.0, 20 ppm regulation, low dropout.
- Serial output rate is adjustable (by DIP switch) from 8.7 to 33.5 SPS averaging.
- Board is designed to work with a 9 k ohm pickup coil.
- Board can be configured for other pickup coils.
- Revised low-noise circuit board is availaible as of December 5, 2005.
- Hammond 1590P diecast enclosure is included for pcb shielding.
- Shielded 9' cable with connector connects the geophone to the circuit board.
- Serial output 10' cable with DB9 female connector for PC COM port.
- Serial extension cables (DB9 M/F) up to 100' are usable for remote sensor locations.
- Serial output rate is 9600 baud, 8N1.
- Serial output ASCII records vary from -32767 to +32767, 0 is zero velocity.
- Power is derived from the PC serial port, and the board turns on when connected.
- Power on board is single-supply 5 volts, current is less than 4 ma @ 5 volts.
- LED Power On indicator blinks at output sampling rate.
- You download Amaseis (freeware) for data logging, helicorder display, data export, etc.
- You download AboutTime (optional/freeware) for time synchronization via Internet.
- You download RighTime (optional/free trial) if you need to adjust Win95/98 PC clock.
- You download WinQuake (optional/free trial) for seismic data analysis.
QM-1.0-3704-Kit Parts list
Figure 1 shows the kit parts:
1 Infiltec QM-1.0-4.5 printed circuit board
2 Diode: Schottkey, 20V, 1A, package DO-41 (1N5817)
2 Resistor 100 Ohm: 1%, 1/4 Watt, metal
1 DB9 serial connector, female, PCB mounting pins
2 Resistor 10k Ohm: 1%, 1/4 Watt, metal
1 Resistor 4.7k Ohm: 1%, 1/4 Watt, metal
2 Resistor 100k Ohm: 1%, 1/4 Watt, metal
6 Capacitor 0.1 uF: ceramic, 50V, 10%, 0.1 inch lead spacing
5 Capacitor 10 uF: tantalum, 10V, 10%, 0.1 inch lead spacing
1 Capacitor 470 uF: electrolytic, 15V, 0.2 inch lead spacing
1 LED: low current (2 ma), 0.1 inch lead spacing
1 Resonator, 4M Hz, built in capacitors, three terminal, 0.1 inch lead spacing (ZTT 4.00mg)
1 Voltage regulator, 5V precision, low drop out, (2950-5.0)
1 Low Pass Filter, 8 pole Bessel filter, DIP8 package (MAX7401CP)
1 Operational Amplifier, low noise, SO8 or DIP8 package (AD8628)
1 Carrier board to convert SO8 to DIP8 (for AD8628)
1 Potentiometer: 10K ohm, three terminal with 0.1 inch lead spacing
1 Capacitor 0.082 uF: 2%, Polypropylene, 50V, 12.5mm lead spacing (
1 DIP switch, 6 position
1 Case: diecast aluminum, (Hammond 1509P)
1 Microcontroller: PIC14000, DIP28, programmed, 16 bit ADC, serial I/O
1 Socket: DIP28 .3" wide
2 Socket: DIP8 .3" wide
1 Conductive tape, copper, 1/2"wide, 2" long, conductive adhesive
1 hookup wire, 24 inches
1 Label for case on adhesive backing
1 Clear overlay with adhesive backing for case label
1 Magnet: alnico, horseshoe, (370-4)
1 Pickup Coil from 220VAC Relay
1 Cable: 10' serial DB9 M/F shielded
1 Cable: 6' stereo audio shielded M/F
1 Capacitor 0.01 uF polypropylene 50V
1 Resistor 10Meg Ohm: 1/2 watt

PCB Serial QM051128 Eratta:
.47k Ohm resistors next to diodes should be 100 Ohm resistors.
470uf electrolytic capacitor is a tight fit between components
Installation of DIP Sockets
Parts:
1 Infiltec QM-1.0-4.5 printed circuit board
1 Socket: DIP28 .3" wide
2 Socket: DIP8 .3" wide
This image shows the 3 DIP sockets soldered to the printed circuit board (PCB). Be sure you have alinged the end with the notch to line up with the "(" or ")" on the PCB.
COMMENT: It is easier to work with the DIP sockets before there are other components on the PCB. It is possible to solder the chips directly onto the board, but using sockets makes it possible to correct mistakes.
Bringing up 12 Volt unregulated DC Power
Parts:
2 Diode: Schottkey, 20V, 1A, package DO-41 (1N5817)
2 Resistor 100 Ohm: 1%, 1/4 Watt, metal
1 DB9 serial connector, female, PCB mounting pins
1 Cable: 10' serial DB9 M/F shielded
This image shows the diodes and 100 Ohm resistors soldered to the PCB along with the DB9 serial cable connector. If you connect the serial cable to your PC and to the PCB serial connector, and start up the Amaseis program to energize the serial port, then you should measure approximately +12 volts between the PCB via labeled Case ground and the leads of either of the 100 Ohm resistors. COMMENT: There is an error in the PCB component label for PCB Serial QM051128 which says .470k Ohms instead of 100 Ohms.
Bringing up 5 Volt regulated DC Power
Parts:
1 Voltage regulator, 5V precision, low drop out, (2950-5.0)
1 Capacitor 0.1 uF: ceramic, 50V, 10%, 0.1 inch lead spacing
1 Capacitor 10 uF: tantalum, 10V, 10%, 0.1 inch lead spacing
1 Capacitor 470 uF: electrolytic, 15V, 0.2 inch lead spacing
This image shows the addition of the precision 5 volt regulator and its 3 related capacitors. If you connect the serial cable to your PC and to the PCB serial connector, and start up the Amaseis program to energize the serial port, then you should measure very close to +5 volts between the PCB via labeled Case ground and the via labeled +5v". COMMENT: There is an error in the PCB Serial QM051128 which places these componts too tightly together. Just squeeze them in and everything will work ok. Note that three of the components have positive and negative leads, so they must be installed in the right orientations: the 470uF and 10 uF capacitors, and the 5v regulator. On the PCB there is a + next to the hole for the positive capacitor leads. And there is a _ that indicates where the flat side of the voltage regulator should be.
Bringing up microprocessor
Parts:
1 LED: low current (2 ma), 0.1 inch lead spacing
1 Resonator, 4M Hz, built in capacitors, three terminal, 0.1 inch lead spacing (ZTT 4.00mg)
1 Resistor 10k Ohm: 1%, 1/4 Watt, metal
1 Resistor 4.7k Ohm: 1%, 1/4 Watt, metal
2 Resistor 100k Ohm: 1%, 1/4 Watt, metal
1 DIP switch, 6 position
1 Microcontroller: PIC14000, DIP28, programmed, 16 bit ADC, serial I/O
1 Capacitor 0.082 uF: 2%, Polypropylene, 50V, 12.5mm lead spacing (
This image shows the addition of the components that are necessary to get the microcontroller running, as indicated by the blinking LED. Install the 4 resistors as indicated on the PCB. Then install the LED with the long leg in the hole indicated by a +. The 0.082 uF capacitor is not polarized, so it can be installed either way. Install the DIP switch so that the numbers are left to right, 1 to 6. Set all the switches to the open position, except for 1 of the 3-6. Switches 3-6 control the data sampling rate. 6 is slowest (8.5 samples per second) and that is the best one for use with the QM-1.0 long period electonics. Install the microcontroller in the DIP28 socket, being careful to orient it properly according notch indicator "(" on the PCB. If you connect the serial cable to your PC and to the PCB serial connector, and start up the Amaseis program to energize the serial port, then the LED should begin to blink. If you set the DIP switch to 3 or 4 or 5 or 6, then you should see the sampling rate change.
Installing the bypass capacitors, chips, and zero pot
Parts:
5 Capacitor 0.1 uF: ceramic, 50V, 10%, 0.1 inch lead spacing
4 Capacitor 10 uF: tantalum, 10V, 10%, 0.1 inch lead spacing
1 Low Pass Filter, 8 pole Bessel filter, DIP8 package (MAX7401CP)
1 Operational Amplifier, low noise, SO8 or DIP8 package (AD8628)
1 Carrier board to convert SO8 to DIP8 (for AD8628)
1 Potentiometer: 10K ohm, three terminal with 0.1 inch lead spacing
This image shows the addition of the bypass capacitors that smooth the 5 volt power at each chip power pin. The .1 uF ceramic capacitors are not polarized and can be installed in any orientation, but the 10 uF tantalum capacitors are polarized and must be installed so that the + lead is in the hole marked +. Note that the + lead on a tantalum is just below the vertical line printed on the side of the capacitor body. The zeroing potentiometer can be installed in any orientation and it comes from the factory in a centered resistance, so it will be close to the proper position without any adjustment. The MAX4701 low-pass filter chip must be installed so that the notch points in the direction indicated by the ")" on the circuit board. The AD8628 amplifier chip is a SOIC8 format surface mount chip, and there is a carrier board that converts SOIC8 to DIP8. The AD8628 is usually supplied as already soldered to the DIP8 carrier board, unless you have specified otherwise. Note that the DIP8 carrier board does not have a notch, so you will have to use the square pin head (pin 1) on the carrier board top to indicate the notched end of the DIP8 socket.
Installing the other filtering components and hookup wires
Parts:
1 Capacitor 0.01 uF polypropylene 50V
1 Resistor 10Meg Ohm: 1/2 watt
1 Resistor 10k Ohm: 1%, 1/4 Watt, metal
1 Capacitor 10 uF: tantalum, 10V, 10%, 0.1 inch lead spacing
1 Conductive tape, copper, 1/2"wide, 2" long, conductive adhesive
1 hookup wire, 24 inches
This image shows the additional filter components and hookup wires. The 0.01 uF capacitor and 10Meg Ohm resistor form a 1.6 Hz low-pass filter and set the gain of the amplifier. These components are not polarized and can be installed in any orientation. The 10k Ohm resistor and 10 uF tantalum capacitor form a 1.6 Hz low-pass filter to remove high frequecy components from the low-pass filter chip. Note that the 10 uF tantalum capacitor is polarized and its positive lead must be in the hole marked with a +. Cut and strip four hookup wires about 6 inches long. The case ground wire is soldered to the via marked case ground. This wire will be connected to the case by a piece of conductive tape. This grounds the PCB to the case and provides EMI shielding. The cable shield wire is soldered to the PCB at the hole marked Cable Shield. This wire is soldered to the top (ground) terminal of the three wire (seteo) socket mounted in the side of the case. The two coil hookup wires are soldered to the PCB at the holes marked Geophone or Coil. These wires are soldered to the two lower (signal) terminals of the three wire (stereo) socket mounted in the side of the case.
Installing the board in the case
Parts:
1 Conductive tape, copper, 1/2"wide, 2" long, conductive adhesive
1 hookup wire, 24 inches
1 Pickup Coil from 220VAC Relay
1 Cable: 6' stereo audio shielded M/F
This image shows how the PCB is installed in the case. The case ground wire is soldered to the via marked case ground. This wire will be connected to the case by a piece of conductive tape. This grounds the PCB to the case and provides EMI shielding. The cable shield wire is soldered to the PCB at the hole marked Cable Shield. This wire is soldered to the top (ground) terminal of the three wire (seteo) socket mounted in the side of the case. The two coil hookup wires are soldered to the PCB at the holes marked Geophone or Coil. These wires are soldered to the two lower (signal) terminals of the three wire (stereo) socket mounted in the side of the case. Cut the female end off the stereo cable and strip off about 1/2" of insulation, exposing the braided shield and two wires. Cut off the braided shield, and strip about 1/4" of the two hookup wires. Solder these two wires to the pickup coil.
Completed QM-1.0 Long Period Seismometer Electronics
Parts:
1 Label for case on adhesive backing
1 Clear overlay with adhesive backing for case label
Write your name on the space provided on the QM-1.0 label. Strip the backing off the clear overlay on cover the label. Cut around the edge of the label. Strip the backing off the adhesive label and apply to the top of the case. This image shows the completed sytem. This image shows the interior of the completed sytem.

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