Mounting the Regulated Feed of the Digilab

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Material Preparation	Regulated Feed of Digilab	Footer

Mounting the Regulated Feed of the Digilab :

In the first part of this practice, you will do the assembly and then test a regulated power supply. This power supply, perfectly integrated with the digilab, will advantageously replace the battery used until now.

Then you will continue the study of digital components by examining shift circuits commonly called shift registers. In English terminology, these are called SHIFT REGISTER (or simply SHIFT.

Shift circuits, formed by a series of cascaded flip-flops, one after the other, are widely used in the processing of digital data. This is the case in the transmission of information in the field of communication. These circuits are also used as counters and memories.

1. - PREPARATION OF HARDWARE

To realize the assemblies and the manipulations envisaged in this practice, you need the following components :

1 power transformer for digilab 220 volts primary and 9 volts secondary

1 bridge rectifier B 40C 3700 / 2200 or equivalent

1 printed circuit for feeding the digilab - Dimension : Length = 11.7 cm and width = 3.9 cm

1 3-wire power cord, (length of your choice)

1 bipolar mains plug with earth

1 chassis fuse holder (see Figure 10)

1 fuse of 220 V - 250 mA

1 red wire clamp socket for chassis (see Figure 9)

1 socket black wire clamp for chassis (see Figure 9)

1 double switch for two-way front panel (see Figure 10)

1 three-way male connector for PCB (see Figure 8)

1 three-way female connector (see Figure 21)

3 terminal blocks with two dominoes (see Figure 17)

2 hexagonal threaded metal spacers Ø 3 - length 9 mm

2 screws Ø 3 x 14 mm countersunk head

2 screws Ø 3 x 4 mm

3 self-tapping screws 3,5 x 9,5 mm

3 self-tapping screws 2,9 x 12,5 mm

2 metal washers Ø 6 x Ø 3,2 mm

4 metal washers Ø 9 x Ø 4,3 mm

1 wide washer

1 ground lug hole Ø 3,2 mm

2 eyelets with thimble hole Ø 4,2 mm

1 electrolytic capacitor of 4700 µF - 25 V

1 tantalum electrolytic capacitor of 4,7 µF - 10 V

1 ceramic capacitor of 100 nF

1 resistance of 220 W 1 / 4 W - tolerance 5 % (red - red - brown - gold)

1 red LED diode Ø 6 mm

1 LED support (see Figure 12)

1 solder roll

1 rigid black insulated wire

1 red isolated rigid wire

1 cable clamp (see Figure 20)

1 soft black wire section 0,5 mm²

1 soft red wire section 0,5 mm²

1 black flexible wire section 0,25 mm²

1 soft red wire section 0,25 mm²

1 soft green wire section 0,25 mm²

1 soupliso Ø 2 mm

1 soupliso Ø 3 mm

1 integrated circuit LM 340T5 or equivalent

1 integrated circuit MM 74C175 or equivalent

1 integrated circuit MM 74C164 or equivalent

1 integrated circuit MM 74C165 or equivalent

2. - REGULAR POWER SUPPLY OF DIGILAB

The regulated power supply which you will wire on the digilab makes it possible to obtain from the AC voltage of 220 volts, a DC voltage of 5 volts. This perfectly regulated voltage has a constant value, independent of the variations of the mains voltage and the current delivered by this same power supply.

Figure 1 illustrates the circuit diagram of the regulated power supply. Let's quickly see how it works.

The mains voltage is applied to the primary of a transformer using a double switch. The 250 mA fuse protects the transformer against overcurrent. The secondary delivers an AC voltage of 9 volts. This voltage, illustrated in Figure 1-a, is rectified by the diode bridge DR1. Then, it is filtered by the electrolytic capacitor C1 of 4700 µF. This makes it possible to obtain at its terminals a DC voltage, the speed of which is indicated in Figure 1.b.

As you can observe, this voltage is not perfectly constant, but has a residual ripple.

In addition, this ripple can increase if the current delivered by the power supply increases. If the mains voltage varies, the average voltage across the capacitor also varies.

To overcome all these disadvantages, you will use the integrated circuit LM 340T5 which is a voltage regulator. On pin 1, it is possible to apply a rectified and filtered voltage of 7.3 volts and 35 volts. Pin 3 is the output and delivers a perfectly regulated voltage of + 5 volts. The maximum output current is 1.5 A.

Capacitors C2 and C3 prevent any oscillations and filter high frequency noise. The LED indicator light indicates whether the power is on or not.

The LM 340T5 controller has a protection circuit against accidental overloads and short circuits at the controller output.

The fuse protects the transformer against a possible short circuit due to the capacitor C1 or the bridge rectifier.

We have mapped the power circuit board shown in Figure 2 to facilitate your practice tasks. The circuit board is relatively simple as you can see.

Perform the various operations with great care and attention and follow the instructions below.

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