Controlling LEDs with Raspberry Pi and BuckPucks

Electronics
#1

Hello all,

Although I have some experience with simple electronics and circuits, I am not as knowledgeable in electrical engineering and need some guidance with a project. I am attempting to individually control 4 LED’s on a Saber Z4 with a Raspberry Pi. I have three, 1000mA BuckPucks, and one 700mA BuckPuck as drivers for them. I also have a laptop DC power supply as a power source.

The LEDs are
POS 1:UV - 395nm; 675mW (LHUV-0395-A065):
POS 2:Red - 43 lm (LXZ1-PD02)
POS 3:Blue - 39 lm (LXZ1-PB01)
POS 4:Green - 118 lm (LXZ1-PM01)

I see that the BuckPucks need a 5V control signal but that a Raspberry Pi pins supply 3.3V, so I am unsure how exactly to figure this out. I would appreciate any advice or help with figuring out how to go about this.

Sincerely,
Nathan

#2

Control Pin Voltage 10V

…according to both of the BuckPuck webpages.

Where did you read 5V?

#3

I was reading this guide on how to control the LED’s from an Arduino. Perhaps the driver component has changed and my understanding was incorrect on the requirements. I suppose I should have read and figured it out better before buying the drivers if this is the case. Although the control voltage may be different, the end goal remains the same.

#4

The only place I see 10v with respect to the control pin is the absolute maximum voltage, not the designed operational response.

It looks like 0V is on, 4.2V or higher is off, and a non linear response curve in between.

Is the goal to have brightness control? Or just on/off? If you want simple on/off, it looks like any of the Pi based relay boards can be used to short ref to ctrl for on/off control. I suspect using a transistor or two wouldn’t be too much more difficult.

#5

Thank you for the information, I did not know that about the control pin. I would like to be able to dim them, preferably through PWM from my Pi if possible. Do you think I could use a transistor connected to my Pi and a power source to feed the proper control voltage to the BuckPuck which would then turn it on and off? If that is possible, would it allow me to pulse the LED’s to adjust brightness? Even if this is the case, please enlighten me with any ideas of going about this that you think would be better.

#6

Dunno if it fills your needs, but the Pixelblaze boards are very useful…

https://www.bhencke.com/pixelblaze1

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#7

That is an interesting device. It seems to be primarily targeted to RGB strips or array boards instead of individual single color LEDs, but I will look into it further and keep it in mind. One reason I would like it to be controlled from my Raspberry Pi is that I also plan to have the Pi control other devices in sync. It seems that the Pixelblaze has wifi control technology that I could utilize for the same purpose, but that might be overkill for my application.

#8

Looks like RaspPi control point already exists here:.

1 Like
#9

Did a very quick look at the buckpuck driver. Looks like it uses one of the industry standards for dimming control - 0-10 Vdc, Several ideas come to mind. You can take the RPi 3.3 pwm to drive a fet / transistor tied to 10 Vdc and feed that to a RC filter to average out the voltage for the control. May need an opamp ckt for the filtering. You’ll need a pwm chnl for each led. Another possibility is to use a digital pot. Some have serial inputs so you might be able to run several dig pots off one serial line. Pot is connected to gnd on one end and +10Vdc on the other. The wiper will be the cntrl voltage.

#10

The digital potentiometer seems to be the more reasonable solution out of the two. Do you have any specific digital pot recommendations that I could implement? I want to make sure that I buy the right parts this time.

#11

Don’t have a specific part. Google “digital pot” to get the manufacturers and then go get their data sheets and app notes. What you’re trying to do w/ RPi has most likely been done. Think 0-10 Vdc is used in some spindle speed cntrl on cnc. RPi forums should have something on how to.