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.*

.. image:: pics/ej-with-pc-lr.jpg
	   :width: 400px


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
:math:`-1` will make it LOW, in both cases
the wave generation is disabled. SQR1 output has a :math:`100~\Omega` **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 5.1\ k\ Ω resistor.

:math:`\pm5\ V` Analog Inputs, A1 & A2:
""""""""""""""""""""""""""""""""""""""""

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

:math:`0 to 5V` 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
-------------------

.. image:: pics/accessory.jpg
	   :width: 400px
	   
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, 1k\ Ω, 2.2k\ Ω , 10k\ Ω , 51k\ Ω and 100 k\ Ω
-  LDR
-  Two silicon diodes (1N4148) and one 3.3 volts zener diode
-  NPN Transistor( 2N2222)

