In this video I am making my second High-CRI LED light orientated for photography and video recording.
Compared to my previously made 72W LED panel ( http://bit.ly/LED72W ) it is way more efficient (same illumination at 50W), is more powerful (100W), has active cooling and is ~35% lighter.
Provided links are affiliates.
Tools You'll Need:
- Drill: https://amzn.to/2U5QQmL
- Threading tool https://amzn.to/2DapkOD (Metric) or https://amzn.to/2DapkOD (Inch)
- Threaded rivet gun https://amzn.to/2PAOxq0
- Acrylic bending tool https://www.instructables.com/id/Acrylic-Bending-...
- Fretsaw https://amzn.to/2Ece851
- Countersink drill bit: https://amzn.to/2WfmMps
- Cheap hole saw bits https://amzn.to/2PEAzn1
- Small utility knife https://amzn.to/2L6Gi2J
- Acrylic cutting knife https://amzn.to/2TZ1645
- Tape measure https://amzn.to/2rfS4Ph
- Diagonal cutting pliers: https://amzn.to/2E8vOz5
- Digital Multimeter https://amzn.to/2rf0EO3
- Wire stripper: https://amzn.to/2E8Qk2W
- Wire cutting pliers https://amzn.to/2rvrL80
- Soldering kit: https://amzn.to/2Q613Bf
- Hot glue gun https://amzn.to/2PdCgpI
Main Materials You'll Need:
- Cree CMT1925 64W LED 3000K CRI 95+ https://amzn.to/2DnHGvq (Typical voltage – 34.2V @ 0.7A, Max – 37.6V, Max current – 1.7A)
- Cree CMT1925 solderless holders https://amzn.to/2GR6rlB
- Heatsink + fan https://amzn.to/2GM0dT3
- Booster module for LEDs https://amzn.to/2Wd7dif
- Step-down / buck module for fans https://amzn.to/2XT3yGG
- Voltmeter/Ammeter 2in1 https://amzn.to/2DE0Bls
- 10k Ohm multiturn potentiometer + cap https://amzn.to/2XT25QA
- 11-inch articulating arm https://amzn.to/2XVqUeN
- High quality 24V 5A power supply https://amzn.to/2GRvIME
- 3mm High Impact Polystyrene (local hardware store)
Other Things You'll Need:
- Wires, heat shrink tubing, electrical tape, nuts, bolts, washers, right angle corners, sandpaper, thermal paste, rubbing alcohol, heat resistant double sided tape, thick double sided tape, thin double side tape.
Video shot with:
- Canon SL2/200D https://amzn.to/2H254k6
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Step 1: Preview
Preview of the project, plus comparison vs my previously made 72W CRI 90+ LED panel.
Full size comparison - http://bit.ly/2UPsCfZ
Step 2: The COB LEDs
For this project I'll be using 2x Cree CXA2530 4000K CRI 90+ LEDs (MAX Limits: 42V, 1.6A, 64W).
As I ordered these a half year ago, now you can find brand new versions like Cree CMT/CMA series LEDs. Like shown in the pictures, there is product option of Premium Color AKA High-CRI (high color rendering index) where minimal CRI is 95+ and typical R9 (measurement of strong red color) is 88-97.
Strong red color is hard to get with good efficiency, so with cheap LEDs skin tones look horrible and unnatural. Meanwhile with R9 of around 90 they look excellent.
You can read more about R9: https://www.waveformlighting.com/tech/what-is-cri-...
So you should use these new LEDs - Cree CMT1925 3000K CRI 95+ (MAX Limits: 37.6V, 1.7A, 64W) - https://amzn.to/2DnHGvq (Item code: CMT1925N0Z0A30H)
Step 3: Power Supply
As LED voltage is around 36V, we can easily achieve that with higher efficiency booster module and 24V 5A power supply. But if we just boost voltage and leave it locked at 36V, we wont be able reduce the brightness.
Step 4: Variable Brightness
So, we need to change constant voltage potentiometer with extended multi-turn potentiometer. With this, we will be able to control the brightness. And with constant current potentiometer we will be able to limit the current. So if current will be limited, voltage will be limited too.
On the boost modules like these, constant voltage potentiometer is 10k Ohms. You can double check in the datasheet ( https://www.bourns.com/pdfs/3296.pdf ) by the code. W103 - 10k Ohms, W502 - 5k Ohms.
For now don't limit the current, just adjust output voltage to around 32V.
Step 5: Mounting LEDs
To cool the LEDs I am using two heatsinks of an old AMD processors. In them we need to drill and thread the holes.
I like to first make one hole, then screw in the holder, mark and make another hole. This way there is less chance to drill inaccurately.
Step 6: MOAR Holes
Same like before, we need to make more holes for the screws which will hold the heatsinks. Always punch drill starting point and use drill bit with a tiny tip in the middle. It makes drilling accurately much easier.
Step 7: On the Heatsink
My holders didn't have solderless connectors, so I needed to solder the wires.
We should apply very thin layer of thermal paste and secure the LEDs.
Step 8: Finishing the LEDs
Now we need to connect LEDs in parallel. Two thin (24 AWG) positive wires connects to one thicker wire, and same thing with negative wires. Heatsinks can be connected with thermal conductive double sided tape and wires grouped with a heat shrink tubing.
Step 9: Making Frame
For the frame I am using 3mm thick high impact polystyrene sheet. This is really nice material to work with. As it is slightly soft - cutting, drilling and thermal bending is really simple. Plus there is almost no chance to crack it while drilling holes. But when cut into smaller pieces it has pretty good stiffness.
I made all bends with my previously made Acrylic Bending Tool - https://www.instructables.com/id/Acrylic-Bending-...
It is cheap and easy to make. It is the must have tool, if you are working with all kinds of plastic materials.
Step 10: LEDs to the Frame
On the front we need to make four holes. I am making 4mm diameter holes and using M3 screws, as it makes aligning much easier due to slight variance in measurement.
I tried to be smart and use life hack style technique.. Results speaks for itself.. Haha.. Just do it "old fashion" way by measuring twice with a ruler.
Step 11: Fixing Frame
So to get properly cut look, I cut middle part, trimmed with utility knife and sanded.
Step 12: Holes Holes Holes Holes Holes
We need to make holes, a lot of holes. One for the potentiometer, many for the air to go in. And then cut window for the voltage and current meter.
Step 13: Assembling Box
To hold two parts very firmly I used metal right angle corners. On the two top corners we need to add threaded rivets, that we could screw on the top cover.
Step 14: Double Sided Tape
In the middle of the box we should add support piece for the 11-inch articulating arm and glue small pieces to lift up the booster module.
Fans can be mounted with thick double sided tape, it will absorb vibration noise from the fans. And if you are skeptical about the double sided tape, please don't be. It will last for a very long time if good quality tape is used with a proper application. Meaning that you always need to clean surfaces with a rubbing alcohol.
My thermometer's double sided tape holds it over 15 year on the outside of the window!
Step 15: Two Holes
Now it is time to make hole for the articulating arm and for power supply cable. And then connect everything together.
Step 16: Connecting Components
As from that wire mess nobody will understand what where is connected, I drew simplified scheme:
First, we need to power the booster, so 24V power supply wires goes to the booster. Also we need to power the fans step-down module from the same 24V source. It will let us adjust fan speed with providing lower voltage like 7V, just make sure to adjust it before connecting into the circuit.
From the same 24V we need to power voltage and current meter’s display with two thin RED and BLACK wires. It has max operating voltage of 30V, so we can’t connect it to the boosted output.
Then POSSITIVE (+) wire from the LEDs goes to the OUT+ connection on the booster. On this same connection, we will need to connect thin white or sometimes yellow wire from the meter. This will give us the output voltage reading.
NEGATIVE (-) wire from the LEDs connects to thick RED wire of the meter. And thick BLACK wire from the meter goes to the booster’s OUT- connection. And now the circuit is complete.
We should glue both modules with thermal conductive double sided tape. As booster module runs very cool at 2.5A, plus it has cooling so it isn't concern at all that it will melt the frame.
Step 17: LIMIT THE CURRENT
Now is THE MOST IMPORTANT STEP in this project:
Make sure current potentiometer is not limiting the current for now.
Make sure voltage is ~32V.
Then, slowly increase the voltage and watch the current.
When you reach desired amps (like 75% of the max Amps), rotate current potentiometer until you see slight drop in the voltage and the current on the display (it might take many turns to do that).
Finally, very slowly increase voltage with the voltage potentiometer and see if it is limited.
If you forget to do that, well RIP LEDs when you apply too much voltage.
Step 18: Finishing Steps
On the top cover we should make many holes that fans would provide good airflow. You can countersink the holes to get excellent look.
Finally, secure the power cable with hotglue and we are done!
Step 19: Light Diffusion
If you don’t like those sharp shadows, you can easily make a very simple light diffuser, which will give you results like in the photo. Just make sure that diffuser parts are further away from the LEDs surface, otherwise they'll melt the diffuser.
Step 20: END
I hope this instructable / video was useful and informative.
If you liked it, you can support me by liking this Instructable / YouTube video and subscribing for more future content. Feel free to leave any questions about this build. Thank you, for reading / watching! Till next time! :)
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