EDL TIPS


With reference to components
----------------------------

The 5W(or higher wattage) resistors (say 4.7 ohms and 2.2 ohms)for loading

the CV,CC and other circuits, are marked as 4E7(4.7 ohms) and 2E2(2.2 ohms).
This is a common practice to replace decimal point with a letter(E,K or M)
to avoide confusion in case the dot is not printed clearly. Thus 2E2 is
2.2 ohm, 4K7 is 4.7Kohm and 5M6 is 5.6Mohm.

You may find the capacitors also marked like this. The capacitor values
are in pf unless marked specifically as uF. Thus 4k7 is 4.7Kpf or 4.7 nF
or .0047uF( fairly confusing??). 33 is 33pf. There are other schemes for
marking. Please check the chart put on the board in the Lab.

Power Transistors will generally have their collectors connected to
casing. If casings of npn and pnp (say SL100 and SK100 in a push-pull

power amplifier)short on the bread-board it may create power supply short

circuit. Keep them at safe distance.
 
If Power ICs heat up, use heat-sinks or reduce power dissipation.

3 Terminal power supplies(7805, 7905...etc) may oscillate if the
decoupling capacitors(see the data sheets) are not used.

Bread-boarding
--------------

Use bus-bar structure on bread-boards as shown below, in order of their
potential to simplify the wiring:

      ---------------------------- +Vcc (White)
      ---------------------------- +5V  (Red)




      ---------------------------- Gnd  (Black)
      ---------------------------- -Vcc (Blue)

Use colour wires for different potentials. Less chances of making mistakes
and  easy to debug. Use the interconnection wires of as short length as
possible, running along the bread-board surface. Cut them as per the need.
Keep unused cut wires in your box. They will save time in future.

Strip the ends of the wires carefully as any cut in the metal core may
lead to wire breaking in the bread-board holes. Do not strip more than 1/4
inch length as longer bare wire may short the board pins if forced in.

The components provided on sticking  tape will have glue stuck to their
ends. Cut the ends( about 1/4 inch)before inserting them in the
bread-board. The glue may  go in the contacts of the bread-board and  
corrode them.

Cut the ends of the components and wires diagonally for easy insertion in
the bread-board.

Clean the connecting wires shining bright with a blade before inserting in
the bread-board. The old wires may have oxide coating which is an
insulator.

Try to lay the components on the bread-board as per the circuit diagram.
Do not twist the component leads to simplify the wiring. Instead modify
the wiring. lay the connecting wires horizontally or vertically only as
far as possible. It gives  good look to the board and also makes it easy
for debuging. Do not take the wires over the ICs as it is difficult to

replace the IC later if you need to.

With reference to uC AT89C2051
------------------------------
Each port pin can sink Max 20 mA but the total current for all output pins
should not be more than 80 mA.

The port pins can not source more than 1 or 2 mA( data not available).
Use buffer if you need to source more than 1 mA current.

THE MICROCONTROLLERS CAN NOT BE TESTED ON THE IC-TESTER KEPT IN THE LAB
***********************************************************************

Pins P1.0 and P1.1 require external pullup. All other pins have internal
pullup.

To use a port for input operation 'FF' must be written to the port first.

For Counter operation pins P3.4 and P3.5 should be configured as
Input pins by writing a 1 in them. The status is latched till a zero is
written.

Upon RESET all interrupts are disabled. To use the interrupts set the
corrosponding bits in IE register. Don't forget to set IE.7 also.

RETI instruction at the end of ISR clears the TF0 and TF1 flags. So they
need not be cleared by programmer.

Default mode on RESET for INT0 and INT1 is 'Level Triggered'.

Minimum 'low' duration for level triggered interrupts is 4 machine cycles.

Low level signal(Interrupts) should be removed from INT0 and INT1 before
RETI instruction in the ISR.

For 'Edge Triggered' interrupts, the interrupt source should be held high
for atleast one machine cycle and low for atleast 1 machine cycle. The
edge is latched by IE0 and IE1 bits in the TCON register. These bits are
automatically cleared by RETI instruction in the ISR. They are not used by
the programmer.

8051/52 are one time programmable. DO NOT USE THEM. Use 89C51/52.
                         __
While using 89C51/52, EA (pin 31, External Access) SHOULD be tied to
+5V if no External Memory is connected to uC. Do not leave it open.

The uC programmer cords are special. They will not work like normal
serial RS 232 cables. Do not remove them from the programmers.

General
-------
The power supply outputs are isolated. Connect common point properly if
your circuit uses more than one supply.

Use proper "Source"(CH1/CH2) for triggering the CRO if the signal is given
to only one channel.

TEK DSO probes have switch for X1 and X10 attenuation. Check the
position before using the probes. Do not use them for function
generator output.

Switch off or disconnect  the function generator connected to your ckt
before switching off the power to the ckt. Failing this may damage the
active device connected to the generator.

Three Terminal power supplies(7805, 7905...etc) may oscillate if the
decoupling capacitors(see the data sheets) are not used.

If Power ICs heat up, use heat-sinks or reduce power dissipation.

Enjoy EDL...