LED Split Printing Enlarger Lamphouse

[Augied]

I used that circuit with a conventional timer, so yes, that arrangement will work. I connected the timer to the mains-input on the 24-volt power supply. The supply had rise- and fall-times that were short enough to be ignored.

Dimming can be done two ways, both using the same DIM wire on the Buck Block drivers:
1. Analog, ranging from 0 volts (off) to 10 volts (full power). You can connect a potentiometer to a resistor divider from the 24v to get this 0-to-10v range.
2. PWM. I used a 555 chip to generate that, which also worked well. A potentiometer let me set the duty-cycle.

My problems were that analog dimming would dim only by about 2.5 stops reliably, and I needed more. And when PWM was added, the Buck Blocks had some thermal drift, making light-level inaccurate.
I settled on using an Arduino microcontroller to generate PWM, and I replaced the Buck Blocks with Mean Well LDD-700 LED-drivers. Much better!
I don't know whether Buck Blocks are still available, but if not (or if they're costly), and you want to use them, I'll ship mine to you for free.

I love the results. LEDs run cool, I can set any contrast I want by changing green/blue ratio, and the diffuser hides small scratches and dust on negatives.

Mark Overton

Could you clarify a few things for me?

Are you saying that the BuckBlocks are aways inaccurate when controlled by PWM, or that the particular PWM implementation you were using had issues? I'm planning to use a Raspberry Pi Pico.

I can't seem to find a clear answer to whether the LDD-700 can by controlled with a 3.3v PWM signal (the Pico doesn't have 5v.) Do you know the answer?

Would 5 XP-E2s for each color running at 700mA be bright enough, or do I need to use the newer ones?

Thanks to everyone on this thread. This is an incredible resource.

 

[koraks]

I can't seem to find a clear answer to whether the LDD-700 can by controlled with a 3.3v PWM signal (the Pico doesn't have 5v.) Do you know the answer?

From the datasheet:

So for the 700mA product, the HIGH level on the pwm pin must be between 3.5V and 8V. The 3.3V output of a Pico will likely be a borderline case that may or may not work, and is therefore not recommended. Use a logic level translator (google it; ready to go modules are plentiful), or DIY a voltage translator with one (inverting) or two (non-inverting) MOSFETs and a couple of resistors. You'll also need a 5V logic supply that you can easily make by feeding the LED supply voltage to an appropriate stepdown converter or linear regulator that is rated for the intended input voltage.

Would 5 XP-E2s for each color running at 700mA be bright enough, or do I need to use the newer ones?

YMMV and it will depend a lot on the enlarger used, the film format you're illuminating, the losses in the diffusion chamber and the sensitivity of the paper you're exposing onto. But the 7W ~ 10W per channel you're proposing will in principle work, but with possibly long exposure times on low contrast grades on slow warmtone B&W paper. For color paper, you'll likely have plenty of light to work with at this power level.

 

[Augied]

From the datasheet:
View attachment 335991
So for the 700mA product, the HIGH level on the pwm pin must be between 3.5V and 8V. The 3.3V output of a Pico will likely be a borderline case that may or may not work, and is therefore not recommended. Use a logic level translator (google it; ready to go modules are plentiful), or DIY a voltage translator with one (inverting) or two (non-inverting) MOSFETs and a couple of resistors. You'll also need a 5V logic supply that you can easily make by feeding the LED supply voltage to an appropriate stepdown converter or linear regulator that is rated for the intended input voltage.


YMMV and it will depend a lot on the enlarger used, the film format you're illuminating, the losses in the diffusion chamber and the sensitivity of the paper you're exposing onto. But the 7W ~ 10W per channel you're proposing will in principle work, but with possibly long exposure times on low contrast grades on slow warmtone B&W paper. For color paper, you'll likely have plenty of light to work with at this power level.

I figured that the answer would be "maybe, but don't count on it."

So the LDD-1000L should work with 3.3V? It sounds like running the XP-E2s at 1000mA will get too hot though, maybe I should go with the newer LEDs.

I print 120 and 4x5, mostly middle grades on neutral paper, so it sounds like I'm ok there.

Exposing my ignorance one more time, how did you come up with 7-10W per channel? Is it forward voltage * amps * number of LEDs?

 

[koraks]

So the LDD-1000L should work with 3.3V?

Looks like it!

It sounds like running the XP-E2s at 1000mA will get too hot though

They're rated for 1200-1500mA, aren't they? It's a matter of sufficient heatsinking and perhaps even some active cooling. This won't be different for other power LEDs; it comes with the territory.

Is it forward voltage * amps * number of LEDs?

You got it
For red, the forward voltage is around 2V, at 700mA this makes 1.4W per LED, so 5 LEDs will be 7W. Green and blue run around 2.8V usually, so that's around 2W per LED and 10W for 5 pcs.
Ignore red for B&W work (obviously).

If there's going to be a power bottleneck, it'll be in the green channel.

 

[Augied]

They're rated for 1200-1500mA, aren't they? It's a matter of sufficient heatsinking and perhaps even some active cooling. This won't be different for other power LEDs; it comes with the territory.

I thought it was 1000mA, but maybe that's an average not the maximum? I'm assuming that using LEDs with a higher rating than the controller is a good idea, but maybe matching the ratings is just fine/better.

The green XP-E2 at 1000mA is 3.7V, so there shouldn't be any bottleneck with a 24V 100W supply (I think) especially since I won't ever run all four colors at once.

 

[Rolleiflexible]

I did just that.

I have attached pictures of the mod and parts. I removed the ring on the bottom of the Beseler 45 Dichroic boxx, the part that mates with the enlarger. I removed the lid frm the mix chamber and mounted the lamp on top. So I am still using the beseler diffuser. Total cost so far is $30 Canadian for the lamp. I will invest a bit more to make it a permanent installation.

https://www.photrio.com/forum/attachments/all-three-jpg.161976/

https://www.photrio.com/forum/attachments/stackup-jpg.161977/

https://www.photrio.com/forum/attachments/lamp-info-jpg.161978/

How has this worked for you? Do you get even illumination across the print? Are you still using it? I like the simplicity.

 

[koraks]

I thought it was 1000mA, but maybe that's an average not the maximum?

Not sure; I just took the numbers from the datasheet:

https://assets.cree-led.com/a/ds/x/XLamp-XPE2.pdf page 3
They should run fine at 1000mA for extended periods of time in an application like an enlarger, which doesn't see hours of continuous use in general anyway.

The green XP-E2 at 1000mA is 3.7V

Around 3V @1A, a little less at lower currents:

there shouldn't be any bottleneck with a 24V 100W supply (I think) especially since I won't ever run all four colors at once.

The blue LEDs with have the highest forward voltage at around 3.2V at 1A. 5 LEDs will still only drop 16V, so a 24V power supply should be fine in combination with an appropriate LED driver.
If you do an RGB system with around 10W each, the power supply will have a generous safety margin, so it should work fine

 

[Augied]

Not sure; I just took the numbers from the datasheet:
View attachment 336006
https://assets.cree-led.com/a/ds/x/XLamp-XPE2.pdf page 3
They should run fine at 1000mA for extended periods of time in an application like an enlarger, which doesn't see hours of continuous use in general anyway.



Around 3V @1A, a little less at lower currents:
View attachment 336007




The blue LEDs with have the highest forward voltage at around 3.2V at 1A. 5 LEDs will still only drop 16V, so a 24V power supply should be fine in combination with an appropriate LED driver.
If you do an RGB system with around 10W each, the power supply will have a generous safety margin, so it should work fine

I was looking at the datasheet from LEDSupply. On closer inpection, that one is rev. 5A, while the one you linked to is rev. 19. Either way, it looks like I'm on the right track now.

 

[L Gebhardt]

From the datasheet:
View attachment 335991
So for the 700mA product, the HIGH level on the pwm pin must be between 3.5V and 8V. The 3.3V output of a Pico will likely be a borderline case that may or may not work, and is therefore not recommended. Use a logic level translator (google it; ready to go modules are plentiful), or DIY a voltage translator with one (inverting) or two (non-inverting) MOSFETs and a couple of resistors. You'll also need a 5V logic supply that you can easily make by feeding the LED supply voltage to an appropriate stepdown converter or linear regulator that is rated for the intended input voltage.


YMMV and it will depend a lot on the enlarger used, the film format you're illuminating, the losses in the diffusion chamber and the sensitivity of the paper you're exposing onto. But the 7W ~ 10W per channel you're proposing will in principle work, but with possibly long exposure times on low contrast grades on slow warmtone B&W paper. For color paper, you'll likely have plenty of light to work with at this power level.

The LLD-700H (and the rest of the LDD-xxxH series) accepts a pwm signal between 2.5 and 6VDC. They also take a higher input voltage so you can drive more LEDs.

Another option is the LDH-45A/B-700 step up driver. It also accepts a low voltage PWM signal.

 

[Augied]

The LLD-700H (and the rest of the LDD-xxxH series) accepts a pwm signal between 2.5 and 6VDC. They also take a higher input voltage so you can drive more LEDs.

Another option is the LDH-45A/B-700 step up driver. It also accepts a low voltage PWM signal.

Interesting, I was under the impression that the only difference between the L and H series was the higher input voltage. This is getting very close to solving all of my problems.

 

[albada]

Could you clarify a few things for me?
Are you saying that the BuckBlocks are aways inaccurate when controlled by PWM, or that the particular PWM implementation you were using had issues? I'm planning to use a Raspberry Pi Pico.
I can't seem to find a clear answer to whether the LDD-700 can by controlled with a 3.3v PWM signal (the Pico doesn't have 5v.) Do you know the answer?
Would 5 XP-E2s for each color running at 700mA be bright enough, or do I need to use the newer ones?
Thanks to everyone on this thread. This is an incredible resource.

Thank you @koraks for answering @Augied's concerns. I'll add my remarks for what they're worth.

BuckBlocks are always inaccurate with PWM having low duty-cycles. For that reason, I recommend Mean Well's drivers instead.
Mean Well's latest drivers are the NLDD-H series. The LDD series is older. The NLDD-H series has models from 350 to 1400 mA, and can accept a PWM signal of 2.5 v or higher, so your Pico will work fine with them.

Cree's latest high-power LEDs are the XE-G series, but I see that LedSupply.com is not yet offering them. You might email or phone LedSupply, asking about whether and when the XE-G will be available on stars. I bought my XE-G LEDs separately from Mouser or Digikey, and bare stars from Cutter Electronics in Australia, and soldered the LEDs onto the stars myself. That's exacting work which I don't recommend. It appears that Cutter is now offering the colors we want on stars. Look here: Cree X-EG at Cutter Electronics .
That gave me 1400 mA LEDs. Actually, they are 3000 mA, but I run them at 1400 mA because they are inefficient above that. So I have ample light. The XP-E2 series of Cree LEDs will be fine, and running them at 700 mA will provide adequate light for most uses. That was my setup for a while, but with encouragement from @koraks, I upgraded my circuitry to XE-G with NLDD-H drivers, and I'm glad I did. As @koraks said, with 700 mA, you'll get longer exposure times with Ilford warmtone paper or large enlargements from 35mm.

Summarizing: I recommend using Mean Well NLDD-H 1400 drivers with Cree XE-G LEDs on stars (from Cutter).

Have fun,
Mark

 

[Augied]

Thank you everyone for the answers and advice. I've been thinking about building an LED head since 2014, but this is the first time that I've felt like I can actually pull it off. Electronics aside, I'm working on what I think is a pretty neat idea for a split grade timer. I've set a goal to have something usable by July, and I'll post progress updates as soon as there's progress to show.

 

[koraks]

@albada thanks for chiming in; I knew you would have essential information to add!
@L Gebhardt thanks also for sharing your experience, currently as well as in the past. It was actually your project with the 138S that encouraged me to try a LED head!

@Augied You can do this Very much looking forward to what you come up with!

 

[albada]

Thank you everyone for the answers and advice. I've been thinking about building an LED head since 2014, but this is the first time that I've felt like I can actually pull it off. Electronics aside, I'm working on what I think is a pretty neat idea for a split grade timer. I've set a goal to have something usable by July, and I'll post progress updates as soon as there's progress to show.

How are you planning to dissipate heat? If your LED head has a max of 60 watts, for example, about 30 watts of heat will need to be dissipated. If you read over page 4 of this thread, you'll see that I used a large aluminum plate to dissipate the heat. A proper heat sink would be smaller and lighter. In any case, you'll need some way to remove that heat.

Could you tell us the basic idea of your timer? We are in suspense...

Mark

 

[L Gebhardt]

One issue I see for me with the NLDD-H series driver is the minimum output voltage is 6, which would affect my use of the driver with a single LED as a point source bulb. Something to also watch out for if you do any testing with a single LED.

Lately I've been using the split grade printing features I built in. It's not perfect as far as the UI, but overall I think f-stop printing with split grade has a lot of merit. For context my print flow looks like:

1) Test strip with green only. Choose the area that will print as just a hint of tone, usually the densest part of the negative.
2) Choose the exposure that gives just a hint of tone
3) Make a test strip with the exposure from above as the base exposure.
- The base exposure is exposed with both blue and green.
- The steps are exposed with only blue light
- The area you choose should ideally include the full range of tones you want in the image
- The steps will show you contrast not overall exposure changes
4) Choose step with correct contrast for the subject
5) Make a full print with 2 exposures:
- a base exposure using the time from step 2 and both blue and green light
- a second exposure with only blue light using the time from 4
6) Determine any dodging and burning you need

Note, I have my system calibrated to different papers and have the ability to dial in the contrast grades. The above requires you to choose a contrast setting that is softer than the overall print requires, based on how my system works. It could be done with totally independent green and blue exposures and test strips.

The reason I like this over regular printing with a fixed contrast per exposure is it allows you to set a base exposure that ensures proper highlights. Then the second test strip allows you to focus on the contrast without affecting the highlights. This is a huge improvement over needing to start over whenever you find you need a different contrast setting. I spend a lot less time chasing my tail.

My caveat with the above is I only just started printing this way in the last few sessions, so I only have a few prints under my belt using it. However the two tricky prints I was struggling with printed easily once I switched to using this method (once I remembered how I implemented it 10 years ago).

 

[Augied]

How are you planning to dissipate heat? If your LED head has a max of 60 watts, for example, about 30 watts of heat will need to be dissipated. If you read over page 4 of this thread, you'll see that I used a large aluminum plate to dissipate the heat. A proper heat sink would be smaller and lighter. In any case, you'll need some way to remove that heat.

I'm going to use an aluminum plate with fins. I haven't decided if I want to attach ready-made fins, or cut them out of the plate myself. A fan that cuts out during exposure is also a possibility if the passive cooling isn't good enough. I operate a CNC and 3d printers for my day job, so I have plenty of flexibility for the enclosure design.

Could you tell us the basic idea of your timer? We are in suspense...

I should have known I couldn't drop that hint and run. Let's see if I can describe my idea so far.

In my college years, I used an Aristo VCL4500 with a Metrolux timer. I want to use that workflow as a base, and make a few improvements, but not over complicate it.

 Hard | Soft | Safe | Focus
 100% | 100% | 100% | 100%
------|------|------|------
  5.5 |  0.0 |  0.0 | +  -
  0.0 |  8.0 |  0.0 | +  -
  3.2 |  0.0 |  2.0 | +  -

Run    +1.0   +0.1
Rst.   -1.0   -0.1
Focus   Up    Enter
Left   Down   Right

The first section is the display, the second is the button arrangement (replacing the numbers on a 3x4 keypad.)

• Navigate through the table with the arrow keys.
• Adjust exposure times with the +/- keys.
• "Run" start/pause exposure. It might be useful to turn on the red light while paused.
• "Rst." stops exposure and/or resets the time.
• If hard and soft times are set, they run together.
• If a safe time is set, run red light before the exposure for burn/dodge preview.
• "Enter" on + adds a new row under the current one. I imagine having space for at least 5 rows.
• "Enter" on - deletes the current row.
• "Focus" toggles white light. Exposure can't be started while white is on.
• Long press "Enter" jumps to light intensity settings.

I think that's it at the moment. Obviously, this only works for split grade printing. I have no interest in calibrating intermediate grades. It might be nice to be able to set different intensities for different burn times, but I can sacrifice in favor of (relative) simplicity.

 

[koraks]

@Augied Not to turn you off of the idea of using push buttons for data entry or anything. I'm sure it works fine. But when I did my enlarger controller/timer unit, I figured that rotary encoders felt a lot more intuitive to me. I don't regret that decision. When I did the first version of my controller, I was regularly using an Ilford 500H, and I always found just twisting the knobs on a regular dichroic head more straightforward. I therefore went with encoders instead. For B&W, I currently use one encoder for contrast grade and the other for time, but my usual way of working is single grade printing. I also have a split grade mode implemented (that I rarely use), which uses a dedicated encoder for low contrast grade, one for low contrast time, and another pair of encoders for high contrast grade and time, respectively. I've never regretted the decision to use encoders for numeric entry.

 

[Augied]

@Augied Not to turn you off of the idea of using push buttons for data entry or anything. I'm sure it works fine. But when I did my enlarger controller/timer unit, I figured that rotary encoders felt a lot more intuitive to me. I don't regret that decision. When I did the first version of my controller, I was regularly using an Ilford 500H, and I always found just twisting the knobs on a regular dichroic head more straightforward. I therefore went with encoders instead. For B&W, I currently use one encoder for contrast grade and the other for time, but my usual way of working is single grade printing. I also have a split grade mode implemented (that I rarely use), which uses a dedicated encoder for low contrast grade, one for low contrast time, and another pair of encoders for high contrast grade and time, respectively. I've never regretted the decision to use encoders for numeric entry.

I started out planning to use rotary encoders, but I was going to need a lot of them to get the features I want. I may still consider some combination of both, rotary encoders for time entry would be much more elegant than the 1.0/0.1 buttons. Right now, I like the keypad because it puts all the controls I need in one place, and it's relatively simple to program.

 

[koraks]

Yeah, I see your point; these are the dilemmas! I've settled on 4 rotary encoders and 8 tactile push buttons in the current interface. I'm not (yet) using the pushbuttons of the rotary encoders.

Btw, it's relatively straightforward to use a rotary encoder for two purposes by distinguishing simply turning it, and turning it while it's pressed down. This is apart from / in addition to the possibility of 'hiding' rotary encoder functionality within menus etc.

 

[albada]

Yeah, I see your point; these are the dilemmas! I've settled on 4 rotary encoders and 8 tactile push buttons in the current interface. I'm not (yet) using the pushbuttons of the rotary encoders.

Btw, it's relatively straightforward to use a rotary encoder for two purposes by distinguishing simply turning it, and turning it while it's pressed down. This is apart from / in addition to the possibility of 'hiding' rotary encoder functionality within menus etc.

I agree with @koraks: Turning a rotary encoder is faster than pushing buttons, making the printing process faster and more enjoyable.

My controller has one encoder. Pressing a button selects an item on the display, making it blink. Turning the encoder changes the selected item. The 24 ticks/revolution encoder changes a number by +-.1 each tick. But pressing it while turning it makes it change by +-.5 or +-1 per tick. If I were to build this controller again, I would use two encoders: One for +-1, and the other for +-.1.

I found it's best to put the encoder near the lower-left corner of the control panel. That placement allows me to turn the encoder with my left hand while pressing buttons with my right hand. That's possible because my left hand is not covering any buttons.

Mark

 

[albada]

I'm going to use an aluminum plate with fins. I haven't decided if I want to attach ready-made fins, or cut them out of the plate myself. A fan that cuts out during exposure is also a possibility if the passive cooling isn't good enough. I operate a CNC and 3d printers for my day job, so I have plenty of flexibility for the enclosure design.

I wish I still had access to a machine shop! You are fortunate. Anyway, Grainger and McMaster sell extruded heat sinks in various widths and lengths, and they state their heat resistances. If I were to do this again, I'd buy one of those instead of my big aluminum plate. You might consider getting one of those.

Mark

 

[Mal Paso]

Some feedback down the road. The chinese 10 turn potentiometers totally failed and regular potentiometers are back in place with a scale of 0-100. I made a test print yesterday with G&B just above LED cut in at 22 for a 15 second exposure at f16 from a 4x5 negative printed 11x14 on Ilford Classic Fiber. Final exposure was 13 seconds at f16 22 Blue 27 Green for a grade of about 2.3. I was able to place the shadows and highlights accurately despite not having real numbered filters. I find the controller totally adequate, will quit fooling with it and print. lol

The print LEDs are about 30W total and dial down about 3.5 stops where it's more than enough for 8x10s. The white LEDs really help with focusing. All I can think of, have fun!