Host Board for Constant Current Hi-Intensity LED Drivers


Senior Member
Just a simple host board for making (playing with) Constant-Current drivers easier & more fun. I didn’t list any code for the Picaxe 60Hz PWM that may be used to build a variable current source as most of y’all already know how to do that.

If anybody uses this stuff to make a programmable battery charger, please share. I’ll get around to that eventually, but I’m retired so I don’t do anything on a schedule. It’s been too rainy & windy to fish, so that’s the reason this little project came about.

1W Version:
10PCS 350mA 1W LED Driver PWM Light Dimmer DC-DC 5-35V Step Down Module

3W Version:
3W 5-35V LED Driver 700mA PWM Dimming DC to DC Step-down Constant Current

XLSEMI XL4001 datasheet datasheet.pdf

While the ebay boards do work just fine for holding the 350mA constant current needed by 1W hi-intensity LEDs, there were a few things I didn’t like:
01 No terminal strips or mounting holes.
02 The PWM input is a little stinky: Using a PWM source, found that the board would supply current in excess of
the 350mA required by the 1W LEDs when PWM was beyond 75%.
03 The PWM input does not work well with hi-frequency PWM. Seems to work best with ~60Hz. However, this works
OK as a dimmer or variable current source. Not a big deal.

The host board doesn’t change a whole lot, just makes it easier to work with:
01 Added terminal strip & mounting holes. Also added 4 2-pin IDC connectors so LEDs can be quickly connected or
removed. Note that since the connectors are in series, a missing LED must have a jumper on it’s connector.
Note also that the terminal strip LED connection should not be used when using the IDC connectors as this would
create a parallel circuit for the current source (would this ever be useful?).
02 Added an open-collector transistor in front of the PWM input. This flips the logic to Hi=ON & Lo=OFF & also lets
the PWM be varied from 0 to 100% without exceeding the 350mA limit for 1W LEDs (so I don’t accidently zap the
connected load when playing with PWM from the Picaxe). A light dimmer shouldn’t burn out the bulbs at full-on!
Don’t forget to use 60Hz PWM frequency.

The board would make an excellent current source for a programmable battery charger when coupled to a Picaxe.
Of course, the Picaxe would need to read the battery voltage & charging current. Need to do this after I get done
with the lighting & alarm applications. Could wind a little shunt & hang it on one of the IDC connectors to pick up
current. A variable current source is handy for controlling pressure or tension, so keep that in mind. Could make a
little dancer roll for keeping line tension constant on my reel winder. Could also be used as a temperature
controller but I’ll need to do a simple PID proc (as used on kayak nav-lock).



Senior Member
PCB Artwork for 3W version of Current Controller

I made up a few circuit boards for the 3W version of the current controllers mentioned in the previous post & they work just like the 1W versions except the current output is 0…700mA (rather than 0…350mA as the 1W versions).

3W Version: TAKE NOTE: mounting holes on this 3W host board slightly off from 1W board
3W 5-35V LED Driver 700mA PWM Dimming DC to DC Step-down Constant Current

While it is possible to use the same PCB artwork for the 3W versions as used for the 1W versions, the Chinese guy who designed the 3W board decided to offset some of the pins by 25 mils. Not a big deal, but it makes mounting the 3W boards onto the 1W host board a little annoying.
Anyhow, for anyone who needs to use the 3W boards, the attached artwork makes for a more exacting fit.
Note: The scaling (hole to hole centers) is only as accurate as your printer. Some apps have printer scaling.

Not sure if anyone else is using a .dxf drill file to let a CNC drill their boards. If so, change the extension on the attached .txt file to .dxf. I always put a reference datum in the lower left-hand corner of the board to let the CNC know where to start. Drilling is from the fiber side of single-sided board.

Note that a CNC .dxf import works best with R12 (arcs & lines) format. Other .dxf formats (e.g. R14) specify lines & circles as a multitude of polylines (working your CNC to death). The proceeding sentence won’t make sense unless you work with CNC. Anyhow, you can view the .dxf in Irfanview to see what I mean (circles should be smooth arcs NOT segmented lines).