Wiring a buckpuck to Arduino

[NightAtTheOpera]

I've already hit a snag in my LED moon phase build. I have no problem with writing the sketch for the Arduino because I'm a software developer but when it comes to putting electronic parts together I'm a total dope. I've googled and googled but can't find the answers so I'm hoping (nix that; praying!) someone here can help me.

 

As far as I can tell a dimmable buckpuck is connected as follows:

 

VIN + and - to power supply.

LED + and - to LEDs.

CTL to digital pin on Arduino (i.e. pin 9)

REF goes to I have no idea where. Can anyone tell me where this wire would go, if anywhere?

 

Also, I'm going to be connecting a DS1307 Real Time Clock to the Arduino. The RTC I'm going to get is from sparkfun electronics; it's already soldered to a breakout board. I know what pins to connect it to on the Arduino but I'm not sure how to connect the wire to the breakout board. Do I just solder the wire into the holes? Here's a link to the DS1307:

 

http://www.sparkfun.com/commerce/product_i...?products_id=99

 

Any help/ideas are appreciated!

[plantarms]

haha i'm right there with you, I actually just ordered the rtc from sparkfun, as well as an lcd screen, and a temperature sensor and I am trying to do the exact same thing! sorry I can't be of any help, i understand most of the programming, but I am well under qualified when it comes to electronics and wiring. i will be keeping an eye on this

[NightAtTheOpera]

You're one step ahead of me; I haven't ordered anything yet since I want to feel pretty confident I can actually do it before spending $$.

 

Hopefully Evil or one of the other electronics/LED gurus will swoop in and save us.

[Vancouver Reefer]

Ok Guys:

 

Looking at the Buckpuck datasheet this is what they suggest. It was the way i was going to use before i made my own drivers:

 

 

You just connect the Arduino to the logic input and use a pwm output pin on the Arduino.

 

 

Here is the link to the datasheet:

 

http://www.leddynamics.com/LuxDrive/datash...21-BuckPuck.pdf

 

 

 

Also here is a pic for the connection of the RTC:

 

 

You can either solder wires dirextly into the holes or solder in a connector and then solder wires to the connector.

 

 

Hope this helps

 

VR.

[evilc66]

^^This

[NightAtTheOpera]

Ok Guys:

 

Looking at the Buckpuck datasheet this is what they suggest. It was the way i was going to use before i made my own drivers:

 

 

You just connect the Arduino to the logic input and use a pwm output pin on the Arduino.

 

 

Here is the link to the datasheet:

 

http://www.leddynamics.com/LuxDrive/datash...21-BuckPuck.pdf

 

 

 

Also here is a pic for the connection of the RTC:

 

 

You can either solder wires dirextly into the holes or solder in a connector and then solder wires to the connector.

 

 

Hope this helps

 

VR.

 

Hi VR:

 

I've looked at the buckpuck datasheet many times but have no skills for reading it! However, I found a post by Evil regarding wiring multiple buckpucks to one pin on the Arduino and if I'm understanding it right:

 

Using an NPN (2N4403) transistor and 5k resistor:

REF to the collector of the transistor, CTRL to the emitter of the transistor.

Base of the transistor to the resistor.

From resistor to Arduino pin.

 

Is that correct?

 

Thanks for the info on how to connect to the breakout board! Question about the pic, though. Are those little squiggly marks representing resistors?

[evilc66]

Sorry, I made a mistake before, and it should be a PNP transistor.

 

 

This is the pin assignments for a PNP. Adjust your connections above accordingly.

[Vancouver Reefer]

Thats correct. You can connect as many buckpucks to the output pin on the arduino. Just make sure you replicate the circuit for each puck. Here is how i was going to connect 2 pucks for actinics on one PWM pin and 2 pucks for the whites on another PWM pin:

 

 

 

Yes those squigly lines are for the pull up resistors needed on the Sparkfun board. Just connect each resistor between the wire on SCL and SDA and +5V of the power supply.

 

VR

[NightAtTheOpera]

You guys have been a great help! Nano-reef.com needs to be nano-reef-plus-electronics-gods.com!

 

Once more thing: I've done some reading and the DS1307 circuit already has pullup resistors. Do I still need to add resistors as shown in the picture? What will happen if I have a resistor where it may not be needed? Will it blow up? (A guy I used to work for thought his computer would blow up if he hit the Enter key at the wrong time and I thought that he was silly for thinking that. What goes around comes around, I guess!)

 

As for the transistor being PNP instead of NPN, does that mean that CTL goes to the collector and the REF to the emittor instead of the other way around?

[evilc66]

CTRL always goes to the base. The base is the actuator for the "switch".

 

There shouldn't be any issues with adding additional pullup resistors to the I2C lines. It's somewhat odd that they have them on the RTC, as there can be many I2C devices on the bus. You only need one pair of pullups on the network.

[NightAtTheOpera]

CTRL always goes to the base. The base is the actuator for the "switch".

 

Thanks for getting back to me, Evil. I'm very confused now about the transistor. Here is the image from a previous post:

 

 

and here is an image from the buckpuck data sheet:

 

 

It looks like the collector is attached to CTRL, the emittor is attached to REF and the base goes to the Arduino so now I'm really confused about what I'm supposed to connect to what. Like I said, I'm a total newbie when it comes to electronics.

 

There shouldn't be any issues with adding additional pullup resistors to the I2C lines. It's somewhat odd that they have them on the RTC, as there can be many I2C devices on the bus. You only need one pair of pullups on the network.

 

I seem to be getting different info on this depending on where I look. Since I know you know your stuff I"m going to add resistors.

[Vancouver Reefer]

Thats correct, Follow the diagram and you cant go wrong!!! All you need to do is mirror the symbol and you have the symbol on the buck puck circuit. Just connect:

 

Collector to CTRL

Emitter to REF

Base to Arduino

 

I seem to be getting different info on this depending on where I look. Since I know you know your stuff I"m going to add resistors.

 

Ive just looked at the Sparkfun RTC module and it does not contain any pull up resistors, so i would connect them in your circuit if it was me.

 

My RTC module has them mounted on the board so i didnt need to add them externally.

[evilc66]

Thanks for getting back to me, Evil. I'm very confused now about the transistor. Here is the image from a previous post:

 

 

and here is an image from the buckpuck data sheet:

 

 

It looks like the collector is attached to CTRL, the emittor is attached to REF and the base goes to the Arduino so now I'm really confused about what I'm supposed to connect to what. Like I said, I'm a total newbie when it comes to electronics.

 

 

 

I seem to be getting different info on this depending on where I look. Since I know you know your stuff I"m going to add resistors.

 

 

Im sorry. Yes, you were right before. I was getting my CTRL and Arduino output confused. Don't mind me

[NightAtTheOpera]

Im sorry. Yes, you were right before. I was getting my CTRL and Arduino output confused. Don't mind me

 

Not a problem, Evil. I appreciate the effort.

 

Today I found out one of my clients is an electrical engineer. He says he will take schematics and draw them out in easy to understand manner that even a noob like me will be able to understand. Between him and all the great folks here at nano-reef I have a great support system for my project.

 

I'm looking forward to the day when I can actually start asking about fish and corals!

[NightAtTheOpera]

Ive just looked at the Sparkfun RTC module and it does not contain any pull up resistors, so i would connect them in your circuit if it was me.

 

My RTC module has them mounted on the board so i didnt need to add them externally.

 

I contacted Sparkfun and they confirmed that each of the 5v pins on the Arduino has a pull up resistor so I won't need on between the RTC and the Arduino. I thought it was mounted on the RTC board itself.

[cwho]

Here is the link to the datasheet:

 

http://www.leddynamics.com/LuxDrive/datash...21-BuckPuck.pdf

 

 

looking at that data sheet, Why wouldn't you just use a connection as in Figure 15 where the Arduino is directly connected to the buckpuck cntrl?

[cptbjorn]

Then afaik you would have to use the LED- pin as your ground reference for the arduino which becomes problematic when you want to add other peripherals, attach a power supply besides the couple ma the REF pin can source, plug in to USB to program it etc.

 

Also I'm not exactly sure what would happen if you attached two buckpuck LED- pins together so that you could use the arduino to dim two or more buckpucks.

[taylorjonl]

Then afaik you would have to use the LED- pin as your ground reference for the arduino which becomes problematic when you want to add other peripherals, attach a power supply besides the couple ma the REF pin can source, plug in to USB to program it etc.

 

Also I'm not exactly sure what would happen if you attached two buckpuck LED- pins together so that you could use the arduino to dim two or more buckpucks.

 

Or you just ground LED-. When I first started using the BuckPucks I recruited my dad(EE), we used an Ohm meter to measure the resistance of LED- and VIN-, it was 0, so we just grounded LED- and all was well with my circuit.

[cptbjorn]

I'm not doubting that it works but are you sure it was zero? The buckpuck probably uses a low value resistor to sense the current through the LED string and between LED- and GND would be one of the best places to put it. It might just be .1 ohms and hard to measure too.

[taylorjonl]

I'm not doubting that it works but are you sure it was zero? The buckpuck probably uses a low value resistor to sense the current through the LED string and between LED- and GND would be one of the best places to put it. It might just be .1 ohms and hard to measure too.

 

My dad was confident that this should be done and I wouldn't doubt him since he has been an EE for 40 years.

[evilc66]

As an EE, he should know better than to do something like that without knowing what is inside a Buckpuck. In many switched inductor buck regulators like this, the LED- does not go directly to ground, and passes through the driver IC. Bypassing that to ground could cause untold problems. If Luxdrive says it's ok, then that's one thing, but I wouldn't assume anything based on what a multimeter tells you.

[pschmitz]

I see NightAtTheOpera hasn't posted for 3 months...

 

But Im still curious how this turned (is turning?) out.

[taylorjonl]

As an EE, he should know better than to do something like that without knowing what is inside a Buckpuck. In many switched inductor buck regulators like this, the LED- does not go directly to ground, and passes through the driver IC. Bypassing that to ground could cause untold problems. If Luxdrive says it's ok, then that's one thing, but I wouldn't assume anything based on what a multimeter tells you.

 

I think this sentence:

 

When using an external power source for the potentiometer, the source ground must be common to the LED- output pin.

 

Along with figure 10 and 13 gave the impression that it could/should be grounded. I am not sure how I can validate this is safe to do but it has worked for myself and my friend. His PWM didn't work until he grounded LED-.

 

I also can't see myself arguing with my dad about this unless I have further details, he has been very helpful and I am the student. Any ideas on how I can validate this assumption?

[evilc66]

I did miss that in the datasheet, so I'm sorry for going off on you (and your dad). Not sure why I did that.

 

My concern was two fold though. First, I have seen far too many buck drivers do odd things when anything but the LED is connected to the LED- side of the circuit. That part of the circuit is typically drained through the chip, so bypassing that can produce odd results. Not all drivers are built this way though. Second, Luxdrive's datasheets are historically inacurate, so I take things like that with a grain of salt.

[taylorjonl]

I sent an email to LEDdynamics asking about it, not sure they will respond. It seems to work in my tests and my friend has been running his wired this way for months, but if it isn't optimal I would like to find out, just not sure how to find out.