I'm using Pin 13 on the UNO (because of it's LED connection on the board) to act as a control line into a 700mA, externally dimmable BuckPuck. I have set up three 1k? resistors that are manually combined in parallel between the Ref and Ctl pins to act as a dimmer for the LED array I have connected to the BuckPuck.
However, when the board is connected to the computer via USB (my voltage regulators for external supply are shot), and the LEDs are powered with a 12VDC wall unit - the board (though running the sketch) is not controlling the BuckPuck (turning it on and off) at the programmed intervals.
Does this have to do with a voltage imbalance? (not enough voltage coming from the output pin to control the BP)
Do the BuckPuck and board have to be on the same power supply? (I wouldn't think they would)
GraemeOh:
I'm using Pin 13 on the UNO (because of it's LED connection on the board) to act as a control line into a 700mA, externally dimmable BuckPuck.
It is usually a good idea to link to the hardware (ideally spec sheet) of the item you are asking about, instead of just assuming people will know (or find) it.
GraemeOh:
I have set up three 1k? resistors that are manually combined in parallel between the Ref and Ctl pins to act as a dimmer for the LED array I have connected to the BuckPuck.
You put 3 1k? resistors in parallel to get 333ohm. Why did you pick that value?
GraemeOh:
However, when the board is connected to the computer via USB (my voltage regulators for external supply are shot), and the LEDs are powered with a 12VDC wall unit - the board (though running the sketch) is not controlling the BuckPuck (turning it on and off) at the programmed intervals.
From the other post, I don't think it has anything to do with the regulator since you aren't seeing the jack's voltage on the Vin node. Which might explain why that same node isn't powering your LEDs or controller.
GraemeOh:
Do the BuckPuck and board have to be on the same power supply? (I wouldn't think they would)
You have to share grounds. It probably isn't a good idea to use the same supply for your Arduino as for the LEDs+Controller.
Also as the datasheet for your BuckPuck says: "Due to the nature of the buck regulator, the input voltage must always be higher than the total forward voltage drop of the LED junction(s) connected in series (2.5V for DC models, 4V for AC models).". Are you trying to power 12V LED modules with a 12V supply? If so, that isn't going to work.
Apologies for the inefficiency of my post - your points were well taken and very helpful.
You put 3 1k? resistors in parallel to get 333ohm. Why did you pick that value?
The resistance can be selected as either 1k, 500 or 330? (1, 2 or 3 in parallel) to supply a gradient based on the dimming rig they send with the BP if you ask for it (which is a 5k pot). This is being built for a person in a genomics lab that is using this specific wavelength to activate a plant protein and these resistance vals gave a good range.
I don't think it has anything to do with the regulator since you aren't seeing the jack's voltage on the Vin node
Am I correct in assuming that the Vin and GND ports under the POWER label serve the same purpose as the DC wall jack does (ie does it also go through the regulator)?
This is my first foray into Arduino, and I'm quite inept.
GraemeOh:
Am I correct in assuming that the Vin and GND ports under the POWER label serve the same purpose as the DC wall jack does (ie does it also go through the regulator)?
There is no regulator between Vin and the Barrel jack. There is a protection diode, however, to prevent damage if you connect the barrel jack with reverse polarity. So if you aren't seeing voltage on Vin then you've either blown the diode or your supply isn't providing positive on the center pin.