Altimeter for Micro-Rockets

Higher and higher!

When dealing with micro-rockets or scale models, it’s often difficult to find out the altitude. The main problem is really the weight of the on-board electronics system, which needs to be as light as possible. This altimeter using SMD components is as light as a letter (16 g) and has a data recorder that lets you record atmospheric pressure every 25 ms up to 16,384 stored values. Once the flight is over, the data are recovered via a serial connection to a computer and displayed in a spreadsheet.

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Materials

100418-PCB.zip

100418-11.zip

Extra info / Update

Features
– SMD throughout
– PIC16F88, programmed in Flowcode V4
– Uses Tiny PIC Bootloader [2]
– ADS1110 16-bit I²C A/D converter
– 32 kB I²C EEPROM memory for around 5 minutes recording time
– MPXH6115A6U pressure sensor
– Powered by a 12 V battery
– Weight: 16–20 g

Correction

Issued: March 31, 2001

IC3 should be an ADS1100-A0, not an ADS1110-A0 as mentioned in the artilce text and shown in the circuit diagram.

Component list

Resistors
R1,R2,R3 = 10kOhm, SMD 1206
R4–R8 = 1kOhm, SMD 1206
Capacitors
C1,C2 = 100?F 16V radial, lead pitch 2.5mm
C3,C4,C5,C7 = 100nF, SMD 1206
C6 = 47nF, SMD 1206
C8–C11 = 1?F 16V radial, lead pitch 2.5mm
Semiconductors
Pressure sensor = MPXH6115A6U (Freescale)
IC1 = PIC16F88-E/SO (SOIC-18), programmed, Elektor # 100418-4
IC2 = 78L05, SOT89
IC3 = ADS1110-A0 (Texas Instruments)
IC4 = 24LC256, SOIC-8
IC5 = ICL232, DIP16
D1–D4 = LED, SMD 1206
D5 = LED, 3mm
Miscellaneous
BATT1= 12V / 50mAh, P23GA
K1 = 3-pin pinheader, lead pitch 0.1 in. (2.54mm)
K2 = 5-pin pinheader, lead pitch 0.1 in. (2.54mm)
K3 = 5-way pinheder socket, lead pitch 0.1 in. (2.54mm)
K4 = 9-way sub-D socket
PCB, main board
PCB, RS-232 interface