Test load help

The most accurate method involves directly measuring the current with an ammeter (or
multimeter set to measure mA). Make sure your meter is rated to handle at least
500mA and that the measurement range is within your intended setting.

a. You can directly attach the multimeter leads to the driver output (red to positive,
black to negative) and power up the driver then adjust the pot to set your
current while monitoring the meter.

b. Another method could be to attach a load (ie rectifier diodes, 1N00x series), if
you want to test a specific output voltage, and then connect the multimeter in
SERIES with the load (red lead to positive driver output, black to one end of the
load, the other end of the load connected to negative driver output).

c. Lastly, you can measure the current while connected to a diode by connecting
the meter in series with the INPUT (red lead to battery positive, black to driver
input positive. Or, you can also do series with the negative side). It is slightly
less accurate as the driver does consume a few mA, but should be relatively
close to actual output.

2. The next accurate method is to measure the voltage across a load.

a. The most simple way is to use a 1 ohm resistor (for 1 ohm, at least 1/4W rating
for up to 500mA, 1W suggested) to make calculations simple, but any resistance
is potentially usable, but you should make it under 10 ohms. Connect the
resistance to the output (one lead to positive, one to negative, any direction),
then power up the driver and measure voltage across the resistor. If you are
using 1 ohm, the measured voltage will be equal to the current, so 1mV will be
equal to 1 mA (1mV = 0.001V). If you’re using a resistance other than 1 ohm,
you can calculate your current with Ohm’s Law, by I = V / R, where I is in Amps
(1A = 1000mA).

b. You can also add rectifier diodes in series with the load to simulate a voltage.
The 1N00x series typically have a 0.7V drop per diode, so 4 is about equivalent to
a red diode and about 6 for a Blu‐ray diode (you can measure their voltage drop
and add/subtract diodes if you need more/less voltage).

3. The last method is the quickest, but also least accurate and involves measuring the
setting resistance on the driver. You can estimate the output current by measuring the
setting resistance between points 1 and 2 in the above picture, then calculate the
output current by the equation: Iout = 1.25 / Rset. Iout is in Amps (1A = 1000mA). You
do not need to power up the driver to do this, so it is the simplest method and only
requires a multimeter. But, most meters lose accuracy as you approach the lower end
of its resistance range, so you may not get an entirely accurate reading which will throw
off your calculations. So, do not use this method if you need an accurate reading of
current or need an accurate current setting.

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bobhaha said:

Taken from the rckstr driver manual



Page 5/6 of the manual
http://sites.google.com/site/rkcstr2/MD_v3_inst_rev1.pdf?attredirects=0

-Adrian

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chipdouglas said:

with the rkcstr, i don't use a test load. i set my dmm t the 2 amp setting and it is accurate to .000 spots. so i connect my leads straight to that.

michael

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Bionic-Badger said:

Those 1N400x rectifier diodes should be able to work well though (use 6 of them in series for a 4.2V drop).

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Bionic-Badger said:

I bought a test load from rkcstr, and the diodes on it were not meant to handle the kinds of currents that the 445nm laser uses (~750mA), so I could smell the plastic cooking. Those 1N400x rectifier diodes should be able to work well though (use 6 of them in series for a 4.2V drop).

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