HMI Components
Edition 07/2012
Series
18
Characteristics
Functions
Market segments
The compact 8 mm Series 18 is especially suited for:
The Series 18 incorporates the following functions:
The EAO Series 18 is especially suited for applications in the segments:
■■ ■■ ■■
Flush design Raised design PCB (with adaptor)
■■ ■■ ■■
Indicator Pushbutton Illuminated pushbutton
■■ ■■
Audio and video Laboratory and measuring equipment
The low level switching element is laid out for low current applications.
Please refer to the EAO website to obtain detailed information regarding this series www.products.eao.com Configure a product to your exact needs and request a quotation.
Content
18 01
Overview
02
Flush design Indicator
320
Pushbutton
322
Illuminated pushbutton
323
04
Indicator
324
10
Pushbutton
326
Illuminated pushbutton
328
Raised design
Accessories
330
Drawings
336
Technical data
337
Application guidelines
338
03
14 17 18 19 22 31 41 44 51 56 57 61 70 71 82 84 92 95 96 97 99 ST
319
18 01
Flush design
Indicator, IP 40
02
Equipment consisting of (schematic overview)
4 max.
03
Lens 18
04 10
Actuator 1
14 17
Product can differ from the current configuration.
30.5
Dimensions [mm]
Additional Information
• Luminosity and wave length variations caused by LED manufacturing processes may cause slight differences regarding the illumination
3 NBY
22
41
Âą
Each Part Number listed below includes all the black components shown in the 3D-drawing. To obtain a complete unit, please select the red components from the pages shown.
Mounting cut-outs [mm]
Lens
Terminal
Part No.
Component layout
Wiring diagram
44
Weight
Plastic red translucent
Solder
18-080.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-080.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-080.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-081.0052
1
1
0.003 kg
Plastic yellow translucent
Solder
18-081.0054
1
1
0.003 kg
Plastic green translucent
Solder
18-081.0055
1
1
0.003 kg
Plastic red translucent
Solder
18-082.0052
1
1
0.003 kg
Plastic yellow translucent
Solder
18-082.0054
1
1
0.003 kg
Plastic green translucent
Solder
18-082.0055
1
1
0.003 kg
51 56
Forward voltage typ.
57 61
Operating voltage
Operation current
Indicator actuator
2.2 VDC @ 20 mA
70
12 VDC
20 mA
71 82
24 VDC
84 92 95 96 97 99 ST
320
page 332
Fixing nut
31
Front bezel set
NJO Âą NN
NJO
19
NJO Y NN
• For front dimensions 19 x 19 mm, Ă˜ 19mm
18
20 mA
Operating voltage
Operation current
Lens
Terminal
Part No.
Wiring diagram
Forward voltage typ.
Component layout
Flush design
18 01 Weight
02 03
Indicator actuator
2.2 VDC @ 20 mA
12 VDC
24 VDC
20 mA
20 mA
Plastic red translucent
Solder
18-060.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-060.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-060.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-061.0052
1
1
0.003 kg
Plastic yellow translucent
Solder
18-061.0054
1
1
0.003 kg
Plastic green translucent
Solder
18-061.0055
1
1
0.003 kg
Plastic red translucent
Solder
18-062.0052
1
1
0.003 kg
Plastic yellow translucent
Solder
18-062.0054
1
1
0.003 kg
Plastic green translucent
Solder
18-062.0055
1
1
0.003 kg
04 10 14 17 18 19
The component layouts you will find from page 336
22 31 41 44
Wiring diagram 1
51 56 57 61 70 71 82 84 92 95 96 97 99 ST
321
18 01
Flush design
Pushbutton, IP 40
02
Equipment consisting of (schematic overview)
4 max.
03
Lens 18
1
04 10 1
14 Additional Information
NJO Y NN
• For front dimensions 19 x 19 mm, Ă˜ 19mm
NJO Âą NN
Front bezel set
page 332
• +/- terminals are not connected NJO
19
Dimensions [mm]
3 NBY
18
Actuator
30.5
17
Product can differ from the current configuration.
page 330
22
Fixing nut
31 41
Âą
Each Part Number listed below includes all the black components shown in the 3D-drawing. To obtain a complete unit, please select the red components from the pages shown.
Mounting cut-outs [mm]
Switching action
Terminal
Part No.
Component layout
Wiring diagram
44 Weight
1 NC
B
Solder
18-188.035
2
1
0.002 kg
C
Solder
18-288.035
2
2
0.002 kg
1 NO
B
Solder
18-187.035
2
3
0.002 kg
C
Solder
18-287.035
2
4
0.002 kg
1 NC
B
Solder
18-168.035
2
1
0.002 kg
C
Solder
18-268.035
2
2
0.002 kg
1 NO
B
Solder
18-167.035
2
3
0.002 kg
C
Solder
18-267.035
2
4
0.002 kg
51 56
Switching system
Contacts
57 61
Pushbutton actuator
Snap-action switching element
70 71 82 84
92 95 96
Pushbutton actuator
Snap-action switching element
Contacts: NC = Normally closed, NO = Normally open Switching action: B = Momentary, C = Maintain The component layouts you will find from page 336
97
2
2
4
4
1
1
1
1
99 ST
Wiring diagram 1
322
Wiring diagram 2
Wiring diagram 3
Wiring diagram 4
Flush design
18 01
Illuminated pushbutton, IP 40
Equipment consisting of (schematic overview)
Lens
02
4 max.
03
page 330 1
18
04 10
Actuator
1
30.5
14
Dimensions [mm]
Product can differ from the current configuration.
17
Additional Information page 332
NJO Y NN
NJO Âą NN
3 NBY
Fixing nut
19 22
Each Part Number listed below includes all the black components shown in the 3D-drawing. To obtain a complete unit, please select the red components from the pages shown.
18
• For front dimensions 19 x 19 mm, Ă˜ 19mm
NJO
Front bezel set
Âą
31 41
Mounting cut-outs [mm]
Contacts
Switching action
Terminal
Part No.
Wiring diagram
Switching system
Component layout
44 51 Weight
56 57
Illuminated pushbutton actuator
Snap-action switching element
1 NC
1 NO
B
Solder
18-188.035
2
1
0.002 kg
C
Solder
18-288.035
2
2
0.002 kg
B
Solder
18-187.035
2
3
0.002 kg
C
Solder
18-287.035
2
4
0.002 kg
61 70 71
82
Illuminated pushbutton actuator
Snap-action switching element
1 NC
1 NO
B
Solder
18-168.035
2
1
0.002 kg
C
Solder
18-268.035
2
2
0.002 kg
B
Solder
18-167.035
2
3
0.002 kg
C
Solder
18-267.035
2
4
0.002 kg
2
92 95
Contacts: NC = Normally closed, NO = Normally open Switching action: B = Momentary, C = Maintain The component layouts you will find from page 336
2
84
96 4
97
4
99 1
Wiring diagram 1
1
Wiring diagram 2
1
Wiring diagram 3
1
ST
Wiring diagram 4
323
18 01
Raised design
Indicator, IP 40
02
Equipment consisting of (schematic overview)
4 max.
03
Lens Ă˜9
04 10
7.2
Actuator
23
14 17
Product can differ from the current configuration.
Dimensions [mm]
Additional Information
19
NJO Y NN
• Luminosity and wave length variations caused by LED manufacturing processes may cause slight differences regarding the illumination
NJO
Each Part Number listed below includes all the black components shown in the 3D-drawing.
Y NN Âą NN
NJO
18
Fixing nut
22
31
Âą
41
Mounting cut-outs [mm]
Forward voltage typ.
Operating voltage
Operation current
Terminal
Part No.
Wiring diagram
51
Component layout
44
Weight
Plastic red translucent
Solder
18-050.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-050.0054
1
1
0.002 kg
Lens
56 57
Indicator actuator, Front dimension 9 x 9 mm
2.2 VDC @ 20 mA
61 70
12 VDC
20 mA
71 24 VDC
20 mA
82
Plastic green translucent
Solder
18-050.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-051.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-051.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-051.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-052.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-052.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-052.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-040.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-040.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-040.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-041.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-041.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-041.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-042.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-042.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-042.0055
1
1
0.002 kg
84 92 95
Indicator actuator, Front dimension 9 x 14 mm
2.2 VDC @ 20 mA
96
12 VDC
20 mA
97 99
24 VDC
ST
324
20 mA
Operating voltage
Operation current
Lens
Terminal
Part No.
Wiring diagram
Forward voltage typ.
Component layout
Raised design
18 01 Weight
02 03
Indicator actuator, Front dimension Ă˜ 9 mm
2.2 VDC @ 20 mA
12 VDC
24 VDC
20 mA
20 mA
Plastic red translucent
Solder
18-030.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-030.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-030.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-031.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-031.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-031.0055
1
1
0.002 kg
Plastic red translucent
Solder
18-032.0052
1
1
0.002 kg
Plastic yellow translucent
Solder
18-032.0054
1
1
0.002 kg
Plastic green translucent
Solder
18-032.0055
1
1
0.002 kg
04 10 14 17 18 19
The component layouts you will find from page 336
22 31 41 44
Wiring diagram 1
51 56 57 61 70 71 82 84 92 95 96 97 99 ST
325
18 01
Raised design
Pushbutton, IP 40
02
Equipment consisting of (schematic overview)
4 max.
03
Lens Ă˜9
04
page 332
10
8.7
Actuator
23
14 Fixing nut Additional Information
NJO Y NN
• +/- terminals are not connected
NJO
Y NN Âą NN
To obtain a complete unit, please select the red components from the pages shown.
NJO
19 22
Each Part Number listed below includes all the black components shown in the 3D-drawing.
31
Âą
41
Mounting cut-outs [mm]
44 51
Switching system
Contacts
Switching action
Terminal
Part No.
Wiring diagram
18
Dimensions [mm]
Component layout
17
Product can differ from the current configuration.
Weight
56 57
Pushbutton actuator, Front dimension 9 x 9 mm
Snap-action switching element
1 NC
61 1 NO
70
B
Solder
18-158.035
2
1
0.002 kg
C
Solder
18-258.035
2
2
0.002 kg
B
Solder
18-157.035
2
3
0.002 kg
C
Solder
18-257.035
2
4
0.002 kg
71 82
Pushbutton actuator, Front dimension 9 x 14 mm
Snap-action switching element
84
1 NC
1 NO
92
B
Solder
18-148.035
2
1
0.002 kg
C
Solder
18-248.035
2
2
0.002 kg
B
Solder
18-147.035
2
3
0.002 kg
C
Solder
18-247.035
2
4
0.002 kg
95 96
Pushbutton actuator, Front dimension Ă˜ 9 mm
Snap-action switching element
97
1 NC
1 NO
99 ST
Contacts: NC = Normally closed, NO = Normally open Switching action: B = Momentary, C = Maintain The component layouts you will find from page 336
326
B
Solder
18-138.035
2
1
0.002 kg
C
Solder
18-238.035
2
2
0.002 kg
B
Solder
18-137.035
2
3
0.002 kg
C
Solder
18-237.035
2
4
0.002 kg
Raised design 2
2
4
18 01
4
02 1
Wiring diagram 1
1
Wiring diagram 2
1
Wiring diagram 3
03
1
04
Wiring diagram 4
10 14 17 18 19 22 31 41 44 51 56 57 61 70 71 82 84 92 95 96 97 99 ST
327
18 01
Raised design
Illuminated pushbutton, IP 40
02
Equipment consisting of (schematic overview)
4 max.
03
Lens Ă˜9
04
page 332
10
8.7
Actuator
23
14 Dimensions [mm] Fixing nut NJO Y NN
18
NJO
22
Each Part Number listed below includes all the black components shown in the 3D-drawing. To obtain a complete unit, please select the red components from the pages shown.
NJO
19
Y NN Âą NN
31
Âą
41 44 51
Switching system
Contacts
Switching action
Terminal
Part No.
Wiring diagram
Mounting cut-outs [mm]
Component layout
17
Product can differ from the current configuration.
Weight
56 57 61
Illuminated pushbutton actuator, Front dimension 9 x 9 mm
Snap-action switching element
1 NC
1 NO
70
B
Solder
18-158.035
2
1
0.002 kg
C
Solder
18-258.035
2
2
0.002 kg
B
Solder
18-157.035
2
3
0.002 kg
C
Solder
18-257.035
2
4
0.002 kg
71 82 84
Illuminated pushbutton actuator, Front dimension 9 x 14 mm
Snap-action switching element
1 NC
1 NO
92
B
Solder
18-148.035
2
1
0.002 kg
C
Solder
18-248.035
2
2
0.002 kg
B
Solder
18-147.035
2
3
0.002 kg
C
Solder
18-247.035
2
4
0.002 kg
95 96 97
Illuminated pushbutton actuator, Front dimension Ă˜ 9 mm
Snap-action switching element
1 NC
1 NO
99 ST
Contacts: NC = Normally closed, NO = Normally open Switching action: B = Momentary, C = Maintain The component layouts you will find from page 336
328
B
Solder
18-138.035
2
1
0.002 kg
C
Solder
18-238.035
2
2
0.002 kg
B
Solder
18-137.035
2
3
0.002 kg
C
Solder
18-237.035
2
4
0.002 kg
Raised design 2
2
4
18 01
4
02 1
Wiring diagram 1
1
Wiring diagram 2
1
Wiring diagram 3
03
1
04
Wiring diagram 4
10 14 17 18 19 22 31 41 44 51 56 57 61 70 71 82 84 92 95 96 97 99 ST
329
18
Accessories
01
Front
02
Lens without LED flush design
03 04 10
Dimension
14 17
Lens
Part No.
Weight
Lens without LED flush design
13.8 x 13.8 mm
18 19
Plastic black opaque
18-982.0
0.001 kg
Plastic red translucent
18-982.2
0.001 kg
Plastic yellow translucent
18-982.4
0.001 kg
Plastic green translucent
18-982.5
0.001 kg
Plastic grey opaque
18-982.8
0.001 kg
Plastic white translucent
18-982.9
0.001 kg
18-962.0
0.001 kg
22 31 41
Lens without LED flush design
Ø 13.8 mm
Plastic black opaque
44 51
Plastic red translucent
18-962.2
0.001 kg
Plastic yellow translucent
18-962.4
0.001 kg
Plastic green translucent
18-962.5
0.001 kg
Plastic grey opaque
18-962.8
0.001 kg
Plastic white translucent
18-962.9
0.001 kg
Part No.
Weight
18-981.2
0.001 kg
56 57 61 70 71
Lens with LED flush design Additional Information • Without built-in series resistor, typical forward voltage 2.2 VDC @ 20 mA • Luminosity and wave length variations caused by LED manufacturing processes may cause slight differences regarding the illumination
82 84
Dimension
Lens
92 95
13.8 x 13.8 mm
96
Lens with LED flush design Plastic red translucent Plastic yellow translucent
18-981.4
0.001 kg
Plastic green translucent
18-981.5
0.001 kg
97 99 ST
Ø 13.8 mm
330
Lens with LED flush design Plastic red translucent
18-961.2
0.001 kg
Plastic yellow translucent
18-961.4
0.001 kg
Plastic green translucent
18-961.5
0.001 kg
Accessories
18 01
Lens without LED raised design
02 Dimension
Lens
Part No.
03
Weight
04 7.5 x 7.5 mm
10
Lens without LED raised design Plastic black opaque
18-952.0
0.001 kg
Plastic red translucent
18-952.2
0.001 kg
Plastic yellow translucent
18-952.4
0.001 kg
Plastic green translucent
18-952.5
0.001 kg
Plastic grey opaque
18-952.8
0.001 kg
Plastic white translucent
18-952.9
0.001 kg
14 17 18 19
7.5 x 12.5 mm
22
Lens without LED raised design Plastic black opaque
18-942.0
0.001 kg
Plastic red translucent
18-942.2
0.001 kg
Plastic yellow translucent
18-942.4
0.001 kg
Plastic green translucent
18-942.5
0.001 kg
Plastic grey opaque
18-942.8
0.001 kg
Plastic white translucent
18-942.9
0.001 kg
31 41 44 51
Ă˜ 7.5 mm
56
Lens without LED raised design Plastic black opaque
18-932.0
0.001 kg
Plastic red translucent
18-932.2
0.001 kg
Plastic yellow translucent
18-932.4
0.001 kg
Plastic green translucent
18-932.5
0.001 kg
Plastic grey opaque
18-932.8
0.001 kg
Plastic white translucent
18-932.9
0.001 kg
57 61 70 71 82 84 92 95 96 97 99 ST
331
18 01 02 03 04
Accessories
Lens with LED raised design Additional Information • Without built-in series resistor, typical forward voltage 2.2 VDC @ 20 mA • Luminosity and wave length variations caused by LED manufacturing processes may cause slight differences regarding the illumination
10 14 Dimension
Lens
Part No.
Weight
17 18 19
Lens with LED raised design
7.5 x 7.5 mm
22
Plastic red translucent
18-951.2
0.001 kg
Plastic yellow translucent
18-951.4
0.001 kg
Plastic green translucent
18-951.5
0.001 kg
31 41
Lens with LED raised design
7.5 x 12.5 mm
44
Plastic red translucent
18-941.2
0.001 kg
Plastic yellow translucent
18-941.4
0.001 kg
Plastic green translucent
18-941.5
0.001 kg
Plastic red translucent
18-931.2
0.001 kg
51 56 57
Lens with LED raised design
Ø 7.5 mm
61 70
Plastic yellow translucent
18-931.4
0.001 kg
Plastic green translucent
18-931.5
0.001 kg
Front bezel
Part No.
Weight
18-920.1
0.006 kg
18-920.2
0.006 kg
18-920.3
0.006 kg
Front bezel set
71 82
Product attribute
Mounting cut-out
84 92 95
for square lens
Front bezel set, flush design, Front dimension 19 x 19 mm 15.8 x 15.8 mm
Plastic black
96 97
for round lens
Front bezel set, flush design, Front dimension 19 x 19 mm 15.8 x 15.8 mm
Plastic black
99 ST
for round lens
332
Front bezel set, flush design, Front dimension Ø 19 mm Ø 16 mm
Plastic black
Accessories
18 01
Blind plug
02
Additional Information • The dimensions of the mounting cut-outs are shown in the product details
03 04
Dimension
Mounting cut-out
Material
Colour
Part No.
10
Weight
14
17
Blind plug
9 x 9 mm
Ø 8 mm
Plastic
black
19-948.0
0.001 kg
18 19
Ø 9 mm
Blind plug Ø 8 mm
Plastic
black
19-949.0
22
0.001 kg
31 41 44 51 56 57 61 70 71 82 84 92 95 96 97 99 ST
333
18
Accessories
01
Rear side
02
PCB plug-in base
9.2
03 04
11.7
3.35
8.8
5.6
14 17
8.8
Dimensions [mm]
Terminal
Part No.
Component layout
18
3.2
9.2
10
11.7
Weight
PCB
18-945
3
0.001 kg
PCB
18-946
4
0.001 kg
19 22
Dimension
pins
31 41
PCB plug-in base
8.8 x 9.2 x 11.7 mm
axial
44 51 56
PCB plug-in base
8.8 x 9.2 x 11.7 mm
right-angled
The component layouts you will find from page 336
57 61 70 71 82 84 92 95 96 97 99 ST
334
Accessories
18
Mounting
01
Lens remover
02 03 04
Part No.
Weight
10 14
Lens remover
18-910
17
0.002 kg
18 Mounting tool
19
Additional Information
22
• For fixing nut long Part No. 19-991
31 41 Part No.
Weight
44 51
19-905
Mounting tool
56
0.011 kg
57 61 70 71 82 84 92 95 96 97 99 ST
335
18 01 02
Drawings
Drawings 9 x 9 mm 19 x 19 mm
03
9 x 14 mm
+
Ø9 mm Ø19 x 19 mm
+
9 x 9 mm 19 x 19 mm
+
+ 1
04
9 x 14 mm
+
X
1
10 14 17 Component layout 1
22
2.54
10.16
+ 1
-
2.54
1.6
2.3
9.2
Component layout 3
57 61 70 71 82 84 92 95 96 97 99 ST
336
2.54
Pins for mounting
8.8
8.8
1
44
56
2.54
+
4x Ø 1.1
51
2x Ø 1.1
2.54
31 41
Drilling plan (element side) Through-connection recommended
Drilling plan (element side) Through-connection recommended
2.54
19
Component layout 2
2.54
18
4x Ø 1.1 11.7
Component layout 4
Ø9 mm Ø19 x 19 mm
Pins for contact / LED
X
+ 1
X
X contact-nr. 2 = NO 4 = NC
Technical data
18 01
Actuator with snap-action switching element Switching system
Electrical characteristics
The snap-action switching system was designed for switching low powers in electronic circuits. Single-break snap-action contact.
Contact resistance ≤ 100 mΩ starting value (initial), as per IEC 60512-2-2b
Material
Electrical life ≥ 500 000 cycles of operation at 30 VDC, 100 mA, as per IEC 60512-5-9c
Lens Polymethylacrylate (PMMA), Polycarbonate (PC)
Power consumption LED 20 mA
Material of contact Gold contact on nickel plating
Switch rating min. 10 μA at 100 μV max. 100 mA at 42 VAC/VDC
Actuator housing Polyamide, colour black
02 03 04 10 14 17 18
Electric strength 500 VAC, 50 Hz, 1 min. between all terminals and earth, as per IEC 60512-2-11
19
Mechanical characteristics Terminals The terminals can be used as soldering terminals. Max. wire diameter: 2 x 0.5 mm² Max. wire cross-section of stranded cable 1 x 0.75 mm² Wire cross-section of terminal 1.6 x 0.4 mm Tightening torque for fixing nut max. 20 Ncm Actuating force 1.4 N Actuating travel 2.2 mm ±0.2 mm Rebound time ≤ 2.5 ms
22
Environmental conditions
31
Storage temperature -40 °C … +80 °C
41
Service temperature -25 °C … +65 °C
44
Protection degree IP 40 front side, as per IEC 60529
51
Shock resistance (Single impacts, semi-sinusodial) 50 g for 11 ms, as per IEC 60068-2-27
56 57
Vibration resistance (sinusoidal) 10 g at 10 – 2000 Hz, amplitude 0.75 mm, as per IEC 60512-4-4
61 70
Mechanical lifetime Momentary action 2 million cycles of operation Maintained action 1 million cycles of operation, as per IEC 60512-5-9a
71 82 84
EAO reserves the right to alter specifications without further notice.
92 95 96 97 99 ST
337
18 01 02 03 04 10 14 17
Application guidelines
Suppressor circuits When switching inductive loads such as relays, DC motors, and DC solenoids, it is always important to absorb surges (e. g. with a diode) to protect the contacts. When these inductive loads are switched off, a counter emf can severely damage switch contacts and greatly shorten lifetime. Fig. 1 shows an inductive load with a free-wheeling diode connected in parallel. This free-wheeling diode provides a path for the inductor current to flow when the current is interrupted by the switch. Without this free-wheeling diode, the voltage across the coil will be limited only by dielectric breakdown voltages of the circuit or parasitic elements of the coil. This voltage can be kilovolts in amplitude even when nominal circuit voltages are low (e. g. 12 VDC) see Fig. 2.
18
22
Switch
ON
31 41
To get an efficient protection, the free-wheeling diode must be connected as close as possible to the inductive load!
Counter EMF over load without free-wheeling diode Fig. 2
Switching with inductive load Fig. 1
19
The free-wheeling diode should be chosen so that the reverse breakdown voltage is greater than the voltage driving the inductive load. The DC blocking voltage (VR) of the free-wheeling diode can be found in the datasheet of a diode. The forward current should be equal or greater than the maximum current flowing through the load.
OFF
0 VDC
44 51 56 57 61 70 71 82 84 92 95 96 97 99 ST
338
+ _
Free-wheeling diode
Inductive load
Several hundred to several thousend volts
di __ e = L dt