modamag
Flashlight Enthusiast
I've always heard the so call high resistance problem of a Mag switch but no one ever told me how high. Well, I finally got some spare time to conduct the test.
=== 1. Parts List ===
- KRM AEEC-300 DC Power Supply
- Fluke 23 Digital Multimeter
- Bel MERIT DX460L Digital Multimeter
- 4x 0.8 Ohm 1W 1% resistor
- 20x Brand New MagD switch
=== 2. Setup ===
The circuit is connected as follows:
Power Supply (+) -- Fluke 23 (200mA mode) -- Alligator clip wire -- Switch -- 4x Resistor in parallel -- Power Supply (-)
Bel Merit is connect in parallel to the (-- Alligator clip wire -- Switch -- Resistor --) to measure the voltage.
=== 3. Test Scenario ===
Case #1: Resistance from the anode spring to the bulb contact point with the spring extended to the maximum height. Sample set of 20x switch randomly selected.
Case #2: Resistance from the anode spring to the bulb contact point with the spring compressed to the miniimum height. Sample set of 20x switch randomly selected.
Case #3: Resistance of the switch core, the part that you slide out of the switch assembly. Sample set of 10x switch with the lowest resistance from earlier test case.
=== 4. Test Result ===
Base Info: the voltage across the Alligator clip & resistor is 1.49 V and the current load is 2.98 A so the total resistance is 0.500 Ohms.
Case #1: Uncompressed Spring
Mean Switch Resistance = 0.045 Ohms
Median Switch Resistance = 0.044 Ohms
Standard Deviation = 0.008 Ohms
complete data set
Case #2: Compressed Spring
Mean Switch Resistance = 0.033 Ohms
Median Switch Resistance = 0.034 Ohms
Standard Deviation = 0.008 Ohms
complete data set
Case #3: Switch Core
Mean Switch Resistance = 0.005 Ohms
Median Switch Resistance = 0.003 Ohms
Standard Deviation = 0.003 Ohms
complete data set
Note: 15% upper and lower outlier ommitted from statistics. All data have been normallized for thermal affect on resistors and wires.
=== 5. Analysis ===
So what does this all mean? Here's couple quickies.
1. If your using a bi-pin slug (incandescent) or ANY PR based adapter such as Diamond LED, you're basically adding 0.05+ Ohms of resistance. It could also be worse (much worse) depending on the oxidation and condition of your switch.
2. You could be loosing the following % in efficiency.
Mag74 (9V @ 3.0A) ... 0.3% - 2.4%
Mag85 (10.5V @ 3.5A) ... 0.3% - 2.4%
LuxIII (K-Vf @ 1.0A) ... 0.8% - 2.0%
The root of all this resistance is from the contact of the switch core to the spring.
I have also check against the connection between the switch core and the housing plate in the back, there is practically no resistance. It seems to make contact very well because of the rigid structure.
=== 6. Remedie ===
Well many of us may already know, but just in case there are newbie or our memory gets away from us.
1. By-pass the spring if you can. Solder directly to the leaf spring of the switch core with the appropriate wire gauge (18G+ for incan, & 24G+ for LEDs).
2. If you have to use the PR socket then try soldering the spring to the can will help, and make sure you thoroughly clean the contacts with alcohol.
3. Make sure the battery anode make good contact with the switch spring.
=== 7. Closing ===
With proper precaution/modification you could easily use the MagD Switch for 100W application. In such case you'll loose ~1W of heat thru the switch contacts.
Also from preliminary analysis the MagC & MagCharger have a slightly "better" switch mechanism but due to lack of sample size I can not conclusively give a verdict.
Editted section #4 & #5 for higher current test which is more applicable to flashlight usage.
=== 1. Parts List ===
- KRM AEEC-300 DC Power Supply
- Fluke 23 Digital Multimeter
- Bel MERIT DX460L Digital Multimeter
- 4x 0.8 Ohm 1W 1% resistor
- 20x Brand New MagD switch
=== 2. Setup ===
The circuit is connected as follows:
Power Supply (+) -- Fluke 23 (200mA mode) -- Alligator clip wire -- Switch -- 4x Resistor in parallel -- Power Supply (-)
Bel Merit is connect in parallel to the (-- Alligator clip wire -- Switch -- Resistor --) to measure the voltage.
=== 3. Test Scenario ===
Case #1: Resistance from the anode spring to the bulb contact point with the spring extended to the maximum height. Sample set of 20x switch randomly selected.
Case #2: Resistance from the anode spring to the bulb contact point with the spring compressed to the miniimum height. Sample set of 20x switch randomly selected.
Case #3: Resistance of the switch core, the part that you slide out of the switch assembly. Sample set of 10x switch with the lowest resistance from earlier test case.
=== 4. Test Result ===
Base Info: the voltage across the Alligator clip & resistor is 1.49 V and the current load is 2.98 A so the total resistance is 0.500 Ohms.
Case #1: Uncompressed Spring
Mean Switch Resistance = 0.045 Ohms
Median Switch Resistance = 0.044 Ohms
Standard Deviation = 0.008 Ohms
complete data set
Case #2: Compressed Spring
Mean Switch Resistance = 0.033 Ohms
Median Switch Resistance = 0.034 Ohms
Standard Deviation = 0.008 Ohms
complete data set
Case #3: Switch Core
Mean Switch Resistance = 0.005 Ohms
Median Switch Resistance = 0.003 Ohms
Standard Deviation = 0.003 Ohms
complete data set
Note: 15% upper and lower outlier ommitted from statistics. All data have been normallized for thermal affect on resistors and wires.
=== 5. Analysis ===
So what does this all mean? Here's couple quickies.
1. If your using a bi-pin slug (incandescent) or ANY PR based adapter such as Diamond LED, you're basically adding 0.05+ Ohms of resistance. It could also be worse (much worse) depending on the oxidation and condition of your switch.
2. You could be loosing the following % in efficiency.
Mag74 (9V @ 3.0A) ... 0.3% - 2.4%
Mag85 (10.5V @ 3.5A) ... 0.3% - 2.4%
LuxIII (K-Vf @ 1.0A) ... 0.8% - 2.0%
The root of all this resistance is from the contact of the switch core to the spring.
I have also check against the connection between the switch core and the housing plate in the back, there is practically no resistance. It seems to make contact very well because of the rigid structure.
=== 6. Remedie ===
Well many of us may already know, but just in case there are newbie or our memory gets away from us.
1. By-pass the spring if you can. Solder directly to the leaf spring of the switch core with the appropriate wire gauge (18G+ for incan, & 24G+ for LEDs).
2. If you have to use the PR socket then try soldering the spring to the can will help, and make sure you thoroughly clean the contacts with alcohol.
3. Make sure the battery anode make good contact with the switch spring.
=== 7. Closing ===
With proper precaution/modification you could easily use the MagD Switch for 100W application. In such case you'll loose ~1W of heat thru the switch contacts.
Also from preliminary analysis the MagC & MagCharger have a slightly "better" switch mechanism but due to lack of sample size I can not conclusively give a verdict.
Editted section #4 & #5 for higher current test which is more applicable to flashlight usage.
Last edited: