I'm still considering my options for a burning laser and decided to do some tests to better understand what to expect if I get the LP 532nm 150mW laser pointer.
LP 515nm 532nm 1-150
The first experiment was to take standard AAA Alkaline Batteries with a heavy load. I used two 12 ohm, 2 watt resistors in parallel to create a 6 ohm, 4 watt resistor. This would be a load of around 500mA at 3 Volts, 417mA at 2.5 Volts, and 333mA at 2.0 Volts.
As expected, the batteries showed 3.06 volts without a load. The second I put the load in place, the voltage dropped to 2.59 volts. With the load removed the batteries slowly recovered most of the starting voltage, but it took some time. After 3 cycles of on/off (),#1 60s on, 60s off, 45 on, 45 off, 45 on) the last cycle showed a loaded starting voltage of 2.56 volts and an ending voltage of 2.48 volts just before the load was removed.
This let me to the next experiment with my 4mW Red laser module. From All Electronics: LASER DIODE MODULE, 650NM 4MW 3VDC | AllElectronics.com
Using a power supply and two meters to measure the voltage and current, I tried several different voltages. The table below shows the results:
Voltage, Current, % of current at 3.0 volts
-----------------------------------------------
3.5V, 23.5mA, 104%
3.4V, 23.1mA, 103%
3.3V, 22.8mA, 101%
3.2V, 22.7mA, 101% Due to rounding some numbers look the same, but they are slightly different.
3.1V, 22.6mA, 100%
3.0V, 22.5mA, 100%
2.9V, 22.2mA, 99%
2.8V, 22.1mA, 98%
2.7V, 21.7mA, 96%
2.6V, 21.6mA, 96%
2.5V, 21.4mA, 95%
2.4V, 21.1mA, 94%
2.3V, 20.7mA, 92% <-- Lowest resistance
2.2V, 19.2mA, 85% <-- This begins the sharp drop in current
2.1V, 11.8mA, 52% <-- Notice the major drop in current
2.0V, 9.0mA, 40%
A voltage like 2.4 volts is only 80% of the voltage of 3.0 volts, but the difference in current is only 94% of 3.0 volts. I believe what I'm seeing is the current limiter trying to keep the current constant across different voltages. While a 150mW green laser module is likely to have a different point of lowest resistance, but I believe the concept holds true.
My third experiment was going to take AAA NiMh batteries and put them under similar load conditions; however I couldn't find any. So I used AA NiMh batteries.
In this test I went for 60 seconds on followed by 60 seconds. With no load the batteries were 2.54 volts. These are batteries that had been in use for a while and were not fully charged. The batteries remained at or very close to their initial load voltage at the end of 60 seconds.
ON 2.26V, OFF 2.53V, ON 2.26V, OFF 2.52V, ON 2.25, OFF 2.51V. With a load of about 377mA, the NiMh batteries held their voltage reasonably well. However, this puts them at the lower part of the voltage current curve in the chart above.
IF a 150mW Green module works the same as my little red Module. NiMh batteries could be used with only a minor loss in power. My past tests with green LEDs has shown me that the green LEDs have about 0.1V higher voltage drop. Thus, NiMh batteries will do only if they are freshly charged and have not been sitting around too long. That 0.1 volt higher voltage drop would put the sharp drop in current at about their operating voltage.
I'll have to get some AAA NiMh batteries and give them a fresh charge under the same test conditions to see how much voltage they'd have.
To Be Continued.....
Bob Diaz
LP 515nm 532nm 1-150
The first experiment was to take standard AAA Alkaline Batteries with a heavy load. I used two 12 ohm, 2 watt resistors in parallel to create a 6 ohm, 4 watt resistor. This would be a load of around 500mA at 3 Volts, 417mA at 2.5 Volts, and 333mA at 2.0 Volts.
As expected, the batteries showed 3.06 volts without a load. The second I put the load in place, the voltage dropped to 2.59 volts. With the load removed the batteries slowly recovered most of the starting voltage, but it took some time. After 3 cycles of on/off (),#1 60s on, 60s off, 45 on, 45 off, 45 on) the last cycle showed a loaded starting voltage of 2.56 volts and an ending voltage of 2.48 volts just before the load was removed.
This let me to the next experiment with my 4mW Red laser module. From All Electronics: LASER DIODE MODULE, 650NM 4MW 3VDC | AllElectronics.com
Using a power supply and two meters to measure the voltage and current, I tried several different voltages. The table below shows the results:
Voltage, Current, % of current at 3.0 volts
-----------------------------------------------
3.5V, 23.5mA, 104%
3.4V, 23.1mA, 103%
3.3V, 22.8mA, 101%
3.2V, 22.7mA, 101% Due to rounding some numbers look the same, but they are slightly different.
3.1V, 22.6mA, 100%
3.0V, 22.5mA, 100%
2.9V, 22.2mA, 99%
2.8V, 22.1mA, 98%
2.7V, 21.7mA, 96%
2.6V, 21.6mA, 96%
2.5V, 21.4mA, 95%
2.4V, 21.1mA, 94%
2.3V, 20.7mA, 92% <-- Lowest resistance
2.2V, 19.2mA, 85% <-- This begins the sharp drop in current
2.1V, 11.8mA, 52% <-- Notice the major drop in current
2.0V, 9.0mA, 40%
A voltage like 2.4 volts is only 80% of the voltage of 3.0 volts, but the difference in current is only 94% of 3.0 volts. I believe what I'm seeing is the current limiter trying to keep the current constant across different voltages. While a 150mW green laser module is likely to have a different point of lowest resistance, but I believe the concept holds true.
My third experiment was going to take AAA NiMh batteries and put them under similar load conditions; however I couldn't find any. So I used AA NiMh batteries.
In this test I went for 60 seconds on followed by 60 seconds. With no load the batteries were 2.54 volts. These are batteries that had been in use for a while and were not fully charged. The batteries remained at or very close to their initial load voltage at the end of 60 seconds.
ON 2.26V, OFF 2.53V, ON 2.26V, OFF 2.52V, ON 2.25, OFF 2.51V. With a load of about 377mA, the NiMh batteries held their voltage reasonably well. However, this puts them at the lower part of the voltage current curve in the chart above.
IF a 150mW Green module works the same as my little red Module. NiMh batteries could be used with only a minor loss in power. My past tests with green LEDs has shown me that the green LEDs have about 0.1V higher voltage drop. Thus, NiMh batteries will do only if they are freshly charged and have not been sitting around too long. That 0.1 volt higher voltage drop would put the sharp drop in current at about their operating voltage.
I'll have to get some AAA NiMh batteries and give them a fresh charge under the same test conditions to see how much voltage they'd have.
To Be Continued.....
Bob Diaz