Some PCB design ideas for DIY LDD-L driver based builds

[Lingwendil]

^ that looks like a good solution, actually! Just need to ground a pin, or run a separate ground (with the power supply, maybe) so that you can use all eight wires to transmit signal..

 

[Kampo]

^ that looks like a good solution, actually! Just need to ground a pin, or run a separate ground (with the power supply, maybe) so that you can use all eight wires to transmit signal..

will need shared ground someplace anyway so powersupply ground will prolly work.

 

[Lingwendil]

Yeah, PSU ground tied together between devices will be needed anyways.

Oh, did a printout and mockup of the Pro boards, and it is really small!



The whole four channel board is barely bigger than a pair of LDD700-H drivers at just 2" square.
I do think we need a different output header solution though, as using the current screw terminals leaves very little room for the head of a screw. I'm debating the best solution. It looks like 2.54mm pin spacing terminals would be a natural solution, but they are a bit pricy. Positive there is that it will be the same pin spacing as the usual header pins, making plug solutions easy.

Hmmm.

 

[Kampo]

nice! always woudnerd why the ldd-l drivers never caught on more. i'm looking at one of the 4 channel boards for my office light re do. I'm looking at doing an esp32 based controller for that build. have one of them coming in the mail to test with the new version of sslac16. looks pretty encouraging, no PCA9685 required!

 

[Lingwendil]

Yeah, I really like the L series. They do however have a few things going against them, they are limited to 36 volts, and 700mA (for the small ones) and the PWM input needs to be at least ~3.5 volts, which rules out direct use with the bluefish mini, and "logic" level PWM, such as the output from the ESP32 and ESP8266. If you want to use the ESP32 based controller you will need a level converter to use the 300-700 L series with them. You'll need two of these for full eight channel functionality- https://www.adafruit.com/product/757

PCA chip solutions will automatically output PWM that is referenced to the supply voltage (typically 5 volts) so no level shifting is needed in most situations when run at typical 5 volt bus power.

I have plans for a six channel board with onboard level shifting (with the BSS138 mosfet) that way direct connection is possible with the bluefish mini, as it is a very common solution for a controller these days. I don't have one to test with, so it's a back burner project for now- unless someone has one they would be willing to donate or lend to science!

I don't see the 700mA on the smaller L as a handicap at all, as very rarely do I run LEDs full blast, and tend to build conservatively in order to get long life out of them. If I need higher output I'll use more LEDs, or a CoB type of solution.

I went and swapped out the output headers on the nano boards for 2.54mm lead spacing terminals, this will allow standard pin header outputs or 2.54mm screw terminals, such as these-
https://www.pololu.com/product/2497
https://www.adafruit.com/product/2141
https://www.mouser.com/ProductDetail/Phoenix-Contact/1725711?qs=sGAEpiMZZMvZTcaMAxB2AF3qQv3QF5c1vOZmEuhjZHU=

Those phoenix ones are expensive, the others are bearable, and generics are available on eBay as well- and may serve us plenty well for this use.



So far I think that the other boards will retain the 5.08mm screw terminal outputs, they are cheap and fit fine with the increased board real estate available there.

 

[Lingwendil]

Looking at connector options for the nano boards, it looks like these will fit, and make it pretty simple to put together a finished harness to run to the LEDs, that way it could be easily disconnected if needed for servicing. It would make for a nice and finished installation in-fixture. Might be useful for those who don't want screw terminals, and they will fit the same pin pattern-

https://www.digikey.com/short/pt0z4w
https://www.digikey.com/short/pt0z4d
https://www.digikey.com/short/pt0zmq

Also, looking at ideas for logic level conversion for use with the Bluefish mini six channel version, I figured the BSS138 would work, as it's what adafruit uses on their converter boards-

https://www.digikey.com/short/pt0z9f

This would allow the bluefish module to be placed onboard, and allow direct connection and control of six drivers. I'll do my best to keep it similar size factor to the 8Up boards, with some onboard stuff to make it all play together nicely , but I need a bluefish to play with for testing before I start on that

 

[theatrus]

What about using an octal line driver (or hex buffer) - 74LS541 or other process families (74LV541) are 5V parts but have CMOS levels at 2V is high.

 

[Lingwendil]

A hex buffer like that seems ideal, actually. I'm outside of my realm of expertise there so parts recommendations are even appreciated!

 

[theatrus]

A hex buffer like that seems ideal, actually. I'm outside of my realm of expertise there so parts recommendations are even appreciated!

The 4504B (from 1980 or so!) would work a treat.

https://www.digikey.com/product-detail/en/MC14504BDR2G/MC14504BDR2GOSCT-ND

TI still sells this in PDIP as well (CD4504B - the datasheet is literally scanned in from some point in the past). I’d use the TTL input mode on the 3V side.

 

[Lingwendil]

That looks perfect! Just need a suitable 5 volt regulator of some sort and we're going to be good. Think the LM1117 types will be fine here?

 

[Macca_75]

It could be done, yes, but I think I would rather do so with a connector that plugs over the pin headers, unless there is sufficient interest to warrant it. After these are finalized I can look into doing a version for it.


Also, as an astute member mentioned via PM, there are a few missing traces on the bottom of the 8Up boards, those have been fixed, somehow they were tied to the GND net and sunk into the ground pour

I am guessing the connector is because you want to board the board into an enclosure.

My current setup (that I am looking to upgrade/replace) has the boards slotted into the MakersLED heatsink. This is why I need the RJ45 connector and not a header (unless you can get RJ45 with the female header) that I could plug straight into it.

 

[Macca_75]

you could always get a RJ45 breakout like this:

could slot right into this you would just need to jumper channel 8 into whatever channel you want it to mirror:

That would work if it were a straight header. I could work with this.

@Lingwendil - what are the dimensions of your board?

 

[Lingwendil]

The four channel boards are 50x50mm, eight channel are 50x100mm. What are the dimensions of the boards you're trying to replace? I have a 6" Maker's sink on my nano, but forget the board slot measurements on them.

EDIT- looks like the Makers Driver boards are 149.45mm wide, so I bet the slots and therefore PCB's are close to that width...

Worse case I can spin off a copy and resize it for you if needed to fit, then you can order a set, and share the extras or just hold onto the extras for future projects

Also, what are the string voltages you are running? If the needed LED voltage is 32 or less, and current per string is 700mA or lower, these may work for you. Six channels, right? I may be able to figure something out for you as a one-off design if you know exactly what pinouts you need, it would be rather simple to make the changes, I just can't guarantee I'll be all that speedy at it

 

[theatrus]

That looks perfect! Just need a suitable 5 volt regulator of some sort and we're going to be good. Think the LM1117 types will be fine here?

LM1117 is 20V input max. If you want this to run off the 36V max rail I’d choose something else, depending on current needs if you want to also run the BlueFish (which is much more power hungry)

 

[Lingwendil]

Hmmmm.

The bluefish module will need the input restricted to 17 volts maximum as it is, unless it's used with a separate regulator or reduced overall voltage, so running a 5 volt regulator that can handle both would be ideal. Any idea what the average current demand is from the bluefish?

 

[Macca_75]

The four channel boards are 50x50mm, eight channel are 50x100mm. What are the dimensions of the boards you're trying to replace? I have a 6" Maker's sink on my nano, but forget the board slot measurements on them.

EDIT- looks like the Makers Driver boards are 149.45mm wide, so I bet the slots and therefore PCB's are close to that width...

Worse case I can spin off a copy and resize it for you if needed to fit, then you can order a set, and share the extras or just hold onto the extras for future projects

Also, what are the string voltages you are running? If the needed LED voltage is 32 or less, and current per string is 700mA or lower, these may work for you. Six channels, right? I may be able to figure something out for you as a one-off design if you know exactly what pinouts you need, it would be rather simple to make the changes, I just can't guarantee I'll be all that speedy at it

Current boards are 99mm wide for a 100mm slot. From memory I have a 48v power supply and am using LDD drivers from 350mA to 1A - would it be possible to make it 1.5A (I have a few of these drivers and my chips are rated to this). No big deal on the 1.5A thing if it can't be done.

6 channels is fine (or reuse whatever you have). If it's a custom job then can I get RJ45 sockets straight on the board? I would be needing 6 so not sure what a batch consists of.

Thanks again.

 

[theatrus]

Hmmmm.

The bluefish module will need the input restricted to 17 volts maximum as it is, unless it's used with a separate regulator or reduced overall voltage, so running a 5 volt regulator that can handle both would be ideal. Any idea what the average current demand is from the bluefish?

The most efficient way would be to use a buck converter. In order to cut costs and make this easy to build, maybe include space to solder in one of the endemic LM2596 modules from eBay/AliExpress?

I wouldn’t run the BlueFish off of a linear regulator from 36V down to 5V, plus a WiFi radio is a >100mA device usually. An NCP781 wouldn’t cut it, and would be quite toasty.

 

[Lingwendil]

Current boards are 99mm wide for a 100mm slot. From memory I have a 48v power supply and am using LDD drivers from 350mA to 1A - would it be possible to make it 1.5A (I have a few of these drivers and my chips are rated to this). No big deal on the 1.5A thing if it can't be done.

6 channels is fine (or reuse whatever you have). If it's a custom job then can I get RJ45 sockets straight on the board? I would be needing 6 so not sure what a batch consists of.

Thanks again.

Unfortunately the LDD-L series only goes up to 36 volts, 700mA max in the footprint that my boards use, the higher current LDD-L drivers are the same size as the LDD-H footprints, but still voltage limited. To use the LDD-H you would need a different board.

A set of boards to do the LDD-H would be what you need, and there are a handful around. I can throw something custom together for you as far as a design, but it may take a week or two at least, then you could order them and assemble yourself easily, with exactly what you need featured on board.

 

[Macca_75]

If you could get the design work I could probably figure out where/how to get it printed and put it together myself.

Any chance you know CIO74 on Reefpi board (or have an account there as I cannot register a new account).

It would seem (at face value) the exact board I am after is in this thread - http://www.reefpi.net/smf/index.php?topic=178.0

Happy to buy the board without the source code.

Alternatively happy if you could sketch it up. Would need to be 6 channels, LDD-H drivers (max 1.5A @56v from memory). Personally I don't need he Bluefish mini to plug in but not sure - that feature may make it more usable to other users.

99mm wide would be ideal to slide into the MakersLED heatsink.

Thx

 

[Lingwendil]

I'm not over there, I've never been into raspberry pi based solutions... I'll have a dig and see what I find over there. There are a few common names I recognize so I might PM some folks.

Alternatively, I can do a custom board design for you too, and PCBs are surprisingly affordable to have made, a typical 100 mm square can be as cheap as 2$USD for ten, plus shipping from JLCPCB.

I'll look more in the morning and get back on here with more comments, I have to pack for a work trip and fly out in the morning, so I might be quiet for a day or so.