The calculator to determine the power supply specifications for LDD drivers has been completed :)
Example screenshot
View attachment 11110
Instructions:
- in the first column, select the type of LDD from the drop down list - options are 300, 350, 500, 600, 700 and 100mA versions. Use one line for each LDD to be connected to the power supply.
- in the second column, enter the numbers of led's to be connected to each LDD.
- in the third column, enter the forward voltage of each led. A default of 3.5v is built into the calculator and will be acceptable for the majority of members.
In the example above (from @
macca_75 current build) the required minimum specifications are 45 volts, 4.15 Amps and 122 Watts. He subsequently purchased a Meanwell GS220A48-R7B which is rated for 48 volts, 4.6 Amps and 220 Watts which exceeds all of the required specifications by a reasonable margin. You should always size power supplies slightly higher than required to limit the supply working at its limit all of the time.
Please note that the LDD drivers will output from 2v to 52v, depending on the power supply - in theory this means that you can operate 1 led off a 48v power supply. I say in theory, as this is not something you necessarily want to do for 2 reasons:
- the excess voltage needs to go somewhere - in this case it will be converted to heat which will need to be dealt with somehow. I plan on running a test on the weekend to see just how much heat is generated.
- the efficiency of the driver is reduced considerably as shown by the following graph taken from the driver specifications
View attachment 11111
You probably don't want to be running less than 4 or 5 off a 48v supply. Thus, as with any type of constant current driver, you need to match the power supply to the number of leds to achieve the greatest efficiency.
One final note in relation to power supplies. There is an inverse relationship between the volts and amps of a PS - to achieve higher volts AND higher amps requires a larger supply, which could be more expensive. It may be possible to use some old laptop power supplies i.e. 18v or 24v just by increasing the number of LDD's and reducing the number of led's on each string. The best bet is to have a play around with the calculator to see what works best.
Cheers
