Operating Manual Ver.1.1

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1 UJT Characteristics Operating Manual Ver.1.1 An ISO 9001 : 2000 company , Electronic Complex Pardesipura, Indore , India Tel : /02, Fax: e mail : info@scientech.bz Website : Toll free :

2 Scientech Technologies Pvt. Ltd. 2

3 UJT Characteristics Table of Contents 1. Introduction 4 2. Theory 6 3. Experiments Experiment 8 Study of the characteristic of Unijunction Transistor (UJT) and to calculate interbase resistance and intrinsic standoff ratio 4. Data Sheet Warranty List of Accessories 12 RoHS Compliance Scientech Products are RoHS Complied. RoHS Directive concerns with the restrictive use of Hazardous substances (Pb, Cd, Cr, Hg, Br compounds) in electric and electronic equipments. Scientech products are Lead Free and Environment Friendly. It is mandatory that service engineers use lead free solder wire and use the soldering irons upto (25 W) that reach a temperature of 450 C at the tip as the melting temperature of the unleaded solder is higher than the leaded solder. Scientech Technologies Pvt. Ltd. 3

4 Introduction is a compact, ready to use UJT Characteristics experiment board. This is useful for students to plot characteristics & various region of operation of UJT. It can be used as stand alone unit with external DC power supply. List of Boards : Model PE02 PE03 PE04 PE05 PE06 PE07 PE10 PE11 PE12 PE13 PE14 PE15 PE16 PE40 PE41 PE42 PE43 PE44 Name MOSFET Characteristics SCR Characteristics TRIAC Characteristics DIAC Characteristics IGBT Characteristics` PUT Characteristics SCR Triggering (R, RC Full wave, RC Half wave) SCR Triggering (UJT) SCR Triggering (IC555) SCR Triggering (IC74121) Ramp and Pedestal triggering SCR Triggering (IC741) SCR Triggering (PUT) SCR Lamp Flasher SCR Alarm Circuit Series Inverter UJT Relaxation oscillator Signal Phase PWM Inverter Scientech Technologies Pvt. Ltd. 4

5 List of other Boards available are : Model ST2701 ST2702 ST2703 ST2704 ST2705 ST2706 ST2707 ST2708 ST2709 ST2710 ST2711 ST2712 ST2713 Name IGBT Characteristics SCR Triggering (R, RC Half wave, RC Full wave) SCR Triggering Techniques Triggering of SCR using IC SCR Lamp Flasher SCR Alarm Circuit Series Inverter Single Phase Controlled Rectifier (With Ramp Comparator Firing Scheme) Single Phase Controlled Rectifier with Cosine Firing Scheme Single Phase Converter Firing Techniques Lamp Dimmer Power Electronics Lab Single Phase Cycloconverter ST2714 ST2715 ST2716 ST2717 ST2718 Speed Control of Universal Motor Using SCR Speed Control of AC Motor Using TRIAC Micro Controller Based Firing Circuit for Controlled Rectifier SCR Commutation Circuits Bedford and Parallel Inverter and many more Scientech Technologies Pvt. Ltd. 5

6 Theory The uni-junction transistor (UJT) is a three terminal device Emitter (E), basel (BI) and base2 (B2). Between basel & base2 it behaves like an ordinary resistance. Rb1 & Rb2 are internal resistance respectively from base 1 & base2. UJT characteristics are very different from the conventional 2 junction, bipolar transistor. It is a pulse generator with the trigger or control signal applied at the emitter. This trigger voltage is a fraction (n) of interbase voltage, Vbb. The UJT circuit symbol and basic construction is shown in figure 1. Its characteristic curve is shown in figure 2. It operates in three different regions : 1. Cut-off region Figure 1 Let voltage Ve be applied between E and B 1 where E is positive with respect to B1. Now increase this voltage from zero upto (Ve < ηv BB ) E to B1 unijunction is reversed bias & emitter current is negative as shown by the curve in figure 2. So upto this when Ve =V BB + V D at point R in figure 1 it operates in cut off region, corresponding voltage & current at this point are Vp (peak voltage) & Ip (peak current). 2. -VE resistance region At point R in figure 1 when Ve= ηv BB + V D emitter starts to inject holes into lower base region B1. This is because of increased number of carrier in base region. So, resistance Rb1 of E-B1 junction decreases. Scientech Technologies Pvt. Ltd. 6

7 Figure 2 Due to this potential at A in figure 2 decrease & current Ie due to voltage Ve increases, so this region is negative resistance region shown by point RS in figure 2. It is a stable region. Decrease in resistance is due to the holes injected into the n- type slab to p-type when conduction is established. 3. Saturation region At point S in figure 2 entire base region is saturated & resistance Rb1 does not decrease any more. This region is called as saturation region. Further increase in Ie is accompanied by voltage Ve where point is called valley point. Voltage and current at this point is called valley voltage (Vv) & valley current (Iv). Scientech Technologies Pvt. Ltd. 7

8 Experiment Objective : Study of the characteristic of Unijunction Transistor (UJT) and to calculate inter base resistance and intrinsic standoff ratio Equipments Needed : 1. Power Electronics Board. 2. DC power supplies + 15 V. 3. Digital multi-meter. 4. 2mm patch multimeter. Circuit diagram : Circuit used to plot different characteristics of unijunction transistor is shown in figure 3 Figure 3 Scientech Technologies Pvt. Ltd. 8

9 Procedure : Connect + 15V DC power supply at their indicated position from external source. 1. To plot the emitter characteristics proceed as follows: 2. Rotate both the potentiometer P 1 and P 2 fully in counter clockwise direction. 3. Connect one voltmeter between test point 6 and ground to read V BB and other between test point 1 and ground to read Ve. 4. Connect ammeter between point 2 and 3 to measure the emitter current Ie and at point 4 and 5 to measure the base current lb. 5. Switch On the power supply. 6. Vary potentiometer P 2 and set a value of voltage V BB = 5 V. 7. Increase the emitter voltage Ve in steps. 8. Keep increasing Ve until it drops on voltmeter, UJT fires and emitter current flows rapidly. 9. Record the corresponding Emitter current for each value of Emitter voltage Ve in an observation table Repeat the above procedure from step 8 for V BB = 10 V and 15 V. 11. Plot the graph of Ve versus Ie with the help of observation table 1. Scientech Technologies Pvt. Ltd. 9

10 Observation Table : Serial Number Emitter Voltage V Emitter current I E at constant value of output voltage V BB = 5V V BB = 10V V BB = 5V Calculations : 1. Interbase Resistance(Rss) It is the sum of resistance between base 1 & base2. R BB = R B1 + R B2 It ranges from 4 to 10 KΩ when Ie = Intrinsic Stand-off Ratio (η) η = R B1 (R B1 + R B2 ) = RB B1 R BB It ranges from 0.51 to Scientech Technologies Pvt. Ltd. 10

11 Data Sheet Scientech Technologies Pvt. Ltd. 11

12 Warranty 1. We guarantee the product against all manufacturing defects for 24 months from the date of sale by us or through our dealers. Consumables like dry cell etc. are not covered under warranty. 2. The guarantee will become void, if a) The product is not operated as per the instruction given in the operating manual. b) The agreed payment terms and other conditions of sale are not followed. c) The customer resells the instrument to another party. d) Any attempt is made to service and modify the instrument. 3. The non-working of the product is to be communicated to us immediately giving full details of the complaints and defects noticed specifically mentioning the type, serial number of the product and date of purchase etc. 4. The repair work will be carried out, provided the product is dispatched securely packed and insured. The transportation charges shall be borne by the customer. For any Technical Problem Please Contact us at List of Accessories 1. 2 mm Patch Cords (Red)...1 No mm Patch Cord (Black)...1 No mm Patch Cord (Blue)...1 No. 4. e-manual...1 No. Updated Scientech Technologies Pvt. Ltd. 12

Operating Manual Ver.1.1

SCR Triggering Techniques ST2703 Operating Manual Ver.1.1 An ISO 9001 : 2000 company 94-101, Electronic Complex Pardesipura, Indore- 452010, India Tel : 91-731- 2570301/02, 4211100 Fax: 91-731- 2555643