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dentex
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Advise about PWM with LDD drivers

Wed Nov 12, 2014 9:55 am

Hello,
I was looking at certain LED drivers by Meanwell, LDD-H: "DC-DC Constant Current Step-Down LED driver"
They looks good, considering also they can be dimmed with PWM.
About this point, I'm not sure they can be run from the RPi, in regards to the voltage during the HIGH state of the cycle:
2014-11-12_105251.jpg
2014-11-12_105251.jpg (26.08 KiB) Viewed 3870 times
Considering that the Gpio pins are at 3.3V, would it work? looking at the image above, from the datasheet, they say "H: >2.5~6VDCor open circuit", so 3.3V should be OK.

Thanks.
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

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joan
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Re: Advise about PWM with LDD drivers

Wed Nov 12, 2014 10:19 am

You can connect ordinary LEDs to a gpio via a resistor and use PWM on the gpio to control the brightness.

You'd have to check the voltage pushed out by your gpios, it may be marginal.

See http://www.mosaic-industries.com/embedd ... ifications

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dentex
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Re: Advise about PWM with LDD drivers

Wed Nov 12, 2014 12:07 pm

Thanks for the input, but I was thinking about a high power LED installation and those drivers seems to be proper, from what I read around. They need an external power supply, i.e. 12V or 24V, and will take care of driving the right number of high power LEDs with constant current (depending on the version: 300mA, 350mA, 500mA, 600mA, 700mA, 1000mA). Sorry if this was not clear in the 1st post.
My doubt regards the voltage available from the gpio pins when they are HIGH during each PWM cycle. According to the image from the datasheet linked above, should be OK.
But just as a confirmation...

Those devices seems to be really of common use, but I didn't found anything on this forum (apart another single thread, saying nothing on PWM).
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

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joan
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Re: Advise about PWM with LDD drivers

Wed Nov 12, 2014 2:14 pm

dentex wrote:Thanks for the input, but I was thinking about a high power LED installation and those drivers seems to be proper, from what I read around. They need an external power supply, i.e. 12V or 24V, and will take care of driving the right number of high power LEDs with constant current (depending on the version: 300mA, 350mA, 500mA, 600mA, 700mA, 1000mA). Sorry if this was not clear in the 1st post.
My doubt regards the voltage available from the gpio pins when they are HIGH during each PWM cycle. According to the image from the datasheet linked above, should be OK.
But just as a confirmation...

Those devices seems to be really of common use, but I didn't found anything on this forum (apart another single thread, saying nothing on PWM).
There isn't much to say about PWM.

There are several gpios which provide specialised PWM. Up to two of those may be used at once. Gpios 12/13 or gpios 18/19 on the A+/B+. Just gpio 18 on the A/B.

All the user gpios can be used for hardware timed PWM or software timed PWM. Hardware timed PWM is good enough for servo positioning, LEDs brightness control, and DC motor speed control. I'd only use software timed PWM for DC motor speed control.

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dentex
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Re: Advise about PWM with LDD drivers

Sat Nov 15, 2014 6:02 pm

Thanks for the reply, I forgot to "watch" the thread.

I meant, in the picture above, under "PWM dimming control" it says H (5V) while below, under "Standard Application" H: >2.5-6VDC or open circuit.

Knowing the gpio pins are 3v3 when "hi", is this the same during a PWM cycle?
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

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joan
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Re: Advise about PWM with LDD drivers

Sat Nov 15, 2014 6:05 pm

dentex wrote:Thanks for the reply, I forgot to "watch" the thread.

I meant, in the picture above, under "PWM dimming control" it says H (5V) while below, under "Standard Application" H: >2.5-6VDC or open circuit.

Knowing the gpio pins are 3v3 when "hi", is this the same during a PWM cycle?
Yes. The gpio will be 3V3 during the on time and 0V during the off time of the PWM cycle.

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dentex
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Re: Advise about PWM with LDD drivers

Sat Nov 15, 2014 6:08 pm

Ok, I guess it will work then. I just have to try.

Thanks.
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

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dentex
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Re: Advise about PWM with LDD drivers

Wed Dec 03, 2014 11:53 am

Hello again,
just as a follow-up, I've built (but still not tested) a DIY board for those LDD-H drivers.
Later on I'll post also how it is going, if it's working or if I've missed anything. :)
Attachments
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Image-03.jpg
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Image-01.jpg
Image-01.jpg (58.81 KiB) Viewed 3569 times
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

JingleBelly
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Joined: Sat Aug 01, 2015 3:40 am

Re: Advise about PWM with LDD drivers

Sat Aug 01, 2015 3:42 am

Did you get this working? I ordered 5 LDD-1000 drivers for my project and I am trying to decide if I can control them with the Pi 3.3v signal or if I need to amp it up to 5v or not.

Thanks!

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dentex
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Re: Advise about PWM with LDD drivers

Sat Aug 01, 2015 4:00 pm

Hello.
Yes, all this stuff is working good.
If you want other details, please take a look at https://github.com/dentex/piac

Bye!
One of my projects with the Raspberry Pi:
--------------------------------------------------------
(Raspberry) Pi Aquarium Controller: https://github.com/dentex/piac

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