The 3 pin IC’s are generally used for LINEAR, FIXED and ADJUSTABLE output voltage regulator applications (FIXED POSITIVE, FIXED NEGATIVE AND VARIABLE TYPES). 78XX series IC regulator have intern overload protection and short circuit current limiting.
Check your 78xx and 79xx series, 3 Pin Voltage Regulator ICs.
Fixed Positive voltage type: 78XX series.
Fixed Negative voltage type: 79XX series.
Adjustable Positive voltage type: LM 338 SERIES.
Adjustable Negative voltage type: LM 337 series.
3 pin Positive voltage regulator (78XX series), Here seven voltage options
Device Type | o/p voltage | Max., I/p voltage Dc |
7805 | 5.0v | 35v |
7806 | 6.0 | 35v |
7808 | 8.0 | 35v |
7812 | 12.0 | 35v |
7815 | 15.0 | 35v |
7818 | 18.0 | 35v |
7824 | 24.0 |
Pin Identification 78xx Data sheet Pdf Details: 7805 to 24V Regulator-datasheet
CIRCUIT DIAGRAM OF 78XX SERIES REGULATOR
HOW TO CHECK YOUR 78XX SERIES REGULATOR?
(DMM) Means Digital MultiMeter
Step-1.
Select Digital MultiMeter Selector Knowb to DIODE MODE,
Connect DMM positive test lead to PIN-1
DMM Negative test lead to PIN-2 = Display reading shows OL DMM READING ( OL MEANS OVER LOAD)
DMM Negative test lead to PIN-3 = Display reading shows OL Step-2.
Connect DMM Negative test lead to PIN-1
DMM positive test lead to PIN-2 = 0.527V OR It means 527 mV
DMM positive test lead to PIN-3 = 0.544VStep-3.
DMM positive test lead to PIN-2
DMM Negative test lead to PIN-1 DISPLAY READING 0.521.v
DMM Negative test lead to PIN-3 DISPLAY READING 0.578.v
Step-4.
DMM Negative test lead to PIN-1
DMM positive test lead to PIN-2 =DISPLAY READING shows OL.
DMM positive test lead to PIN-3 = DISPLAY READING shows OL
Step-5.
DMM Positive test lead to PIN-3
DMM Negative test lead to PIN-1 Display Reading shows 0.538v
DMM Negative test lead to PIN-2 READING shows OL
Step-6.
DMM Negative test lead to PIN-3
DMM positive test lead to PIN-1 =DISPLAY READING shows OL.
DMM positive test lead to PIN-2 = DISPLAY READING shows 0.578V.
Verification: If the DMM above reading shows the condition is GOOD.
3 pin Negative voltage regulator (79XX series)
The 79XX type are 3 terminal negative voltage regulators (complements to the 78xx series device)
9-OPTIONS BELOW
Device Type | o/p voltage | Max., I/p voltage Dc |
7902 | -2.0v | -35v |
7905 | -5.0 | -35v |
7905.2 | -5.2v | -35v |
7906 | -6.0 | -35v |
7908 | -8.0 | -35v |
7912 | -12.0 | -35v |
7915 | -15.0 | -35v |
7918 | -18.0 | -35v |
7924 | -24.0 | -40 |
Pin Identification 79xx Data Sheet Pdf Details: 7905 Negative Regulator-datasheet
Step-1. Select Digital MultiMeter Selector Knowb to DIODE MODE,
DMM Negative test lead to PIN-2 = Display reading shows OL DMM READING ( OL MEANS OVER LOAD)
DMM Negative test lead to PIN-3 = Display reading shows OL
Step-2.
Connect DMM Negative test lead to PIN-1
DMM positive test lead to PIN-2 = 0.507 V OR It means 507mV
DMM positive test lead to PIN-3 = 0.634V
Step-3.
DMM positive test lead to PIN-2
DMM Negative test lead to PIN-1 DISPLAY READING 0.508.v
DMM Negative test lead to PIN-3 dISPLAY READING 0.505.v
Step-4.
DMM positive test lead to PIN-2 =DISPLAY READING shows OL.
DMM positive test lead to PIN-3 = DISPLAY READING shows OL
Step-5.
DMM Negative test lead to PIN-1 Display Reading shows 0.638v
DMM Negative test lead to PIN-2 READING shows OL
Step-6.
DMM positive test lead to PIN-1 =DISPLAY READING shows OL.
DMM positive test lead to PIN-2 = DISPLAY READING shows 0.508V.
Verification: If the DMM above reading shows the condition is GOOD.
Positive Adjustable voltage Regulator – LM 338.
An adjustable voltage regulator a single IC satisfies many voltage requirements from 1.2v to 57v and Current is 0.4A To 1.5A Input DC voltage 65V.
It consist of 3 terminals like; Data Sheet For ADJ +ve Type
LM317 Pin Details Pdf: LM317 Positive Regulator-datasheet
1. ADJUSTMENT (ADJ)
2. OUTPUT.
3. INPUT.
Package Types are;
Metal can Package TO-3 STEEL TO-39 METAL
Negative Adjustable voltage Regulator – LM 337.
An adjustable voltage regulator a single IC satisfies many voltage requirements from -1.2v to -57v and Current is 0.4A To 1.5A, Input DC voltage 65V.
It consist of 3 terminals like; Data Sheet For ADJ -ve Type
LM 378 Pin Details Pdf: LM337 Negative Regulator-datasheet
1. ADJUSTMENT (ADJ)
2. OUTPUT.
3. INPUT.
Plastic package LM338 Data sheet pdf : LM338-Regulator-datasheet
HOW TO CHECK YOUR ADJUSTABLE NEGATIVE REGULATOR? LM 338.
helpful. thanx
So helpful. This is not connected what if powered?
Hi Your testing instructions for 78XX & 79XX voltage regulators, using a DMM, appear to be wrong, because Step 2 and Step 4 contradict each other. In both steps the negative lead is connected to Pin 1 with the positive lead being applied to Pin 2 and Pin 3. However, in Step 2 a mV reading suggests a GOOD regulator whereas in Step 4 an OL reading suggests a GOOD one.
Should Step 4 have the negative lead on Pin 2 with the positive lead then applied to Pin 1 & Pin 3 giving an OL in each case?
Thanks for your test,it so helpful,but some steps make contraction here so you should careful,all in all i appreciate your work..!!!!
OL means “Open Line”, NOT “Overload”