# The equipment

ExpEYES Junior is interfaced and powered by the USB port of the computer, and it is programmable in Python. It can function as a low frequency oscilloscope, function generator, programmable voltage source, frequency counter and data logger. For connecting external signals, it has connectors on the top panel. as shown in the figure below. The software can monitor and control the voltages at these terminals. Inorder to measure other parameters (like temperature, pressure etc.), we need to convert them in to electrical signals by using appropriate sensor elements. Even though our primary objective is to do experiments, you are advised to read through the brief description of the equipment given below. The device can be also used as a test equipment for electrical and electronics engineering experiments.

IMPORTANT :

The external voltages connected to ExpEYES Junior must be within the allowed limits. Inputs A1 and A2 must be within ±5 volts range and Inputs IN1 and IN2 must be in 0 to 5V range. Exceeding these limits may result in damage to the equipment. To measure higher voltages, scale them down using resistive potential divider networks.

# External connections

The functions of the external connections briefly explained below. All the black coulored terminals are at ground potential, all other voltages are measured with respect to it.

## Input and Outputs:

### Constant Current Source (CCS) :

The constant current source can be switched ON and OFF under software control. The nominal value is 1.1 mA but may vary from unit to unit, due to component tolerances. To measure the exact value, connect an ammeter from CCS to GND. Another method is to connect a known resistance (~1k) and measure the voltage drop across it. The load resistor should be less than 2k for this current source.

### Programmable Voltage (PVS) :

Can be set, from software, to any value in the 0 to +5V range. The resolution is 12 bits.

### Square Waves SQ1 and SQ2:

Output swings from 0 to 5 volts and frequency can be varied 4Hz to 100kHz. All intermediate values of frequency are not possible. Setting frequency to 0Hz will make the output HIGH and setting it to − 1 will make it LOW, in both cases the wave generation is disabled. SQR1 output has a 100Ω series resistor inside so that it can drive LEDs directly. SQ2 is similar to SQ1 but it has no series resistor inside.

### Digital Output (OD1) :

The voltage at OD1 can be set to 0 or 5 volts, using software.

### SINE, oscillator output:

Frequency is around 150Hz and amplitue around 4V.

### Capacitance meter IN1:

Capacitance connected between IN1 and Ground can be measured. It works better for lower capacitance values, upto 10 nanoFarads, results may not be very accurate beyond that.

### Frequency Counter IN2:

Capable of measuring frequencies upto several MHz.

### Resistive Sensor Input (SEN):

This is mainly meant for sensors like Light Dependent Resistor, Thermistor, Photo-transistor etc. SEN is internally connected to 5 volts through a 5.1kΩ resistor.

### ±5 V Analog Inputs, A1 & A2:

Can measure voltage within the ±5 volts range. The maximum sampling rate is 250 ksps total.

### 0to5V Analog Inputs, IN1 & IN2:

Can measure voltage within the 0 to 5 volts range.

### Microphone output MIC:

A condenser microphone is fixed on the unit and it's amplified output is available on MIC.

# 1.2.2 Accessory Set

To get started, a set of accessories are provided with expEYES.

- Pieces of wires, with pin and with crocodile clip.
- Condenser microphone with leads.
- Inductor Coil (2) : 44SWG wire on 1cm dia bobbin. Around 3000 Turns (some may have more turns). These coils can be used for studying inductance, electromagnetic induction etc.
- Piezo Electric Discs (2) : Resonant frequency is around 3500 Hz. Can be energized by WG output or SQR1. Discs are enclosed in a plastic shell that forms a cavity, that enhances the amplitude of sound produced.
- DC Motor : Should be powered by a DC voltage less than 3 volts.
- Permanent Magnets : (a) 10mm dia & length (b) 5 mm dia & 10 mm length (c) Button size magnets(2)
- 5mm LEDS : RED, BLUE, GREEN, WHITE
- Capacitors : 100pF, 0.1uF , 1 uF & 22uF
- Inductor : 10 mH / 20Ω,
- Resistors : 560Ω, 1kΩ, 2.2kΩ , 10kΩ , 51kΩ and 100 kΩ
- LDR
- Two silicon diodes (1N4148) and one 3.3 volts zener diode
- NPN Transistor( 2N2222)