Fran 🇦🇷The holes are for the switch, the cable, and the vertical rod. The one for the rod ended a bit loose; drilling it with a 10 mm bit to fit a 10 mm rod was too optimistic. Next time, I'm going to use a 3/8" drill bit and sand the end of the rod until it fits just right.
This is the circuit diagram for the lamp, which will be powered from a USB charger.
The LED is a Bridgelux BXRE-30S0801-D-7X with a CRI of 98 and 3000 K. It is a 6 watt LED, but I'm going to use it at 4.85 watt to extend its lifetime.
The power on the USB port is 5 volts, which is not enough to turn on this LED that needs 17.15 volts. That's why I use a voltage booster (the green board), which converts 5 volts to 18 volts.
🧵 #PortuariaLamp #lamp #prototype #LED #USB #electronics #DIY
And the 4.85 watts that the LED will be working at come from this calculation:
led_voltage * current = led_power
17.15 volts * 0.283 amps = 4.85 watts
This way of connecting an LED is fairly simple, but it is not used much because the excess voltage from the supply to the LED is wasted as heat in the resistors. The trick to minimizing this loss of efficiency is to not have the supply voltage be much higher than the voltage to the LED, as in this circuit.
The energy wasted as heat in this circuit would be:
(supply_voltage - led_voltage) * current = power_in_the_resistor
(18 volts - 17.15 volts) * 0.283 amps = 0.24 watts
That is, between LED and resistor we have a total of:
4.85 watts + 0.24 watts = 5.09 watts
And of which the energy wasted in the resistor is 0.24 watts / 5.09 watts * 100 = 4.7%, more than acceptable for such a "primitive" circuit 🤷♂️.
One issue with this shameless display of the heatsink is that it should at least be left more or less presentable for that. Normally the heatsinks are hidden inside the luminaire because they are considered ugly and not very aesthetic, but that is an idea I do not share, as you can see in my other prototypes 😁.
This is how the heatsink comes from the manufacturer, and sometimes they come worse than that with steps from the sawing.
f it is going to be hidden, it is enough to level only the part where the LED will make contact so that it has good thermal transfer. But here it is part of the visual of the product, so I proposed to leave it as mirrored as possible.
The steps were 220 grit sandpaper, fine sanding sponge, superfine sanding sponge, and rubber abrasive block (I have no idea what grit these last three are).
Putting the heatsink so exposed also has a technical reason; doing that maximizes the air flow through the heatsink, which reduces the working temperature of the LED and extends its useful life.
It would need one more step with some finer grit, because the scratching is still a bit visible, but it turned out pretty mirror-like compared to how it was initially 💪.
Shellac is my favorite finish for wood. Some reasons for this are:
- It is of biological origin, since it is obtained from the secretion of an insect from Southeast Asia.
- It can be diluted in ethyl alcohol, a relatively safe solvent also of biological origin.
- It is not toxic, it is even an authorized food additive under code E904.
- Easy to apply and repair locally if it gets scratched.
- Biodegradable in reasonable times.
Shellac is sold in flakes to dissolve or in a ready-made solution with alcohol. In both cases it has a limited storage time of one to two years. In the case of flakes, what happens is that it polymerizes and then no longer dissolves in alcohol.
It already happened to me with a batch of flakes that were left unused for two years. With the next batch I bought, I set out to prevent the same thing from happening to me again.
I read that you can extend the shelf life by lowering the temperature and humidity the flakes are exposed to, so the plan was to seal portions with silica gel in vacuum-sealed packs, store the packets in an airtight glass jar, and store the jar in the refrigerator.
Two years have passed and the flakes from that batch still completely dissolve in alcohol in just two hours, as if they were freshly harvested 🥳.
The time has come to assemble the base. The idea is to have a printed circuit board with the voltage booster, resistors, and connectors for the LED and the switch, and at the same time to act as a cover for all the wiring.
Sending the printed circuit board to be manufactured in China as usual implies a delay of at least a month in the mail, so I decided to improvise something with a blank board. It didn't turn out so bad 😁.
First working prototype of the Portuaria Lamp! 💪
Although it is a desk lamp, I will be using it as a bedside lamp to test the mechanical stability against being hit in the dark.
There are still several things to improve:
- The cotton-covered cable gets very linty and stains very easily.
- The ceramic screen also needs modifications. I can see the screws 😱.
- Making the vertical axis of the lamp perfectly square is hard 🤯.
🧵 #PortuariaLamp #lamp #woodenlamp #woodworking #LED #productdesign
Trying other cable colors. I got some colored polyester cords (plastic 😱) to cover the lamp cable. The idea is to solve two problems that the white cotton cord has: it gets very linty and stains very easily.
Of the four, I chose the orange one because I thought it was the one that best matched the wood of the base. I took the whole lamp apart, reassembled the LED cable with the orange cord, put the orange cable in the lamp... and I didn't like how it turned out 🤪🤦♂️.
What I didn't like is how the contrast between the orange cable and the wood of the rods looks. I had only compared it with the wood of the base before putting it on and it looked good, but the wood of the rods being lighter and with less grain is totally overshadowed by the striking orange cable.
So I took it all apart again and put the grey cord on, which doesn't conflict with the wood of the rods... but now the lamp is very sober and boring! 😂.
Keep trying 🤷♂️.
I'm working on a new screen for the prototype. This time custom made instead of recycling what was lying around from previous projects.
The things this new screen design aims to improve are:
- Ease of assembly. Placing the LED in place while tightening the screws was no fun at all 🤯.
- Mounting the LED with connectors instead of soldering it, to make it easier to repair 🛠.
- Avoiding the cable and screws being visible through the gap between the heatsink and the screen.
- Improving the airflow through the heatsink by creating a chimney effect.
🧵 #PortuariaLamp #lamp #prototype #productdesign #ceramics #lampdesign
This task is kind of delayed because the clay is sabotaging the perfect circularity of my pieces 😂.
Because of the unorthodox shape for a ceramic piece, the circle dries unevenly and ends up becoming an ellipse 🤨.
Slow drying over several days didn't work either. So I turned to the wisdom of r/Ceramics on Reddit to see how I could fix it and they threw out a few ideas that I need to try.
To be continued...
🧵 #PortuariaLamp #lamp #prototype #ceramics #lampdesign #productdesign
I made a USB cable that matches the cable I put in the lamp 😎.
It only has two conductors because it will be used to send power and does not need the data pins, if someone wants to use it to transfer data they will be in for a disappointment 😁 (probably the me of the future 🤦♂️).
The white tubes are heat shrinkable tubes that come coated with glue inside. I have not grey heat-shrink in stock, so I used a white one that was around here 🤷♂️.
The heat shrink on the USB-A side turned out pretty good because the metal USB plug gives it shape, but on the USB-C side it turned out kind of a mess because there is nothing uniform underneath. I am still quite happy with the results of this improvised technique to assemble USB plugs.
Working on the second prototype, now with more angles for greater pleasure 😂.
In the previous prototype, making the cutouts in the round rods and aligning the holes turned out to be quite complicated. And the result didn't convince me much either, because it had a more crafty style than a designer lamp one 🤨.
So to change the look and simplify the manufacturing, I tried using square and rectangular rods.
I made them different on purpose, to add contrast between the rods. Making the vertical rod rectangular also helps prevent the wood from bending due to the weight of the lamp head.
And look who's back, the orange cable! Because I like how it matches the eucalyptus wood rods.
Another reason to use eucalyptus wood instead of "palo blanco" wood for the rods is that, as with all other native woods in Argentina, everyone cuts them down and no one replants them 👀.
The LED is running at 48.6 C. Pretty good considering the maximum operating temperature is 105 C 🥳.
What's not so good is the voltage regulator temperature, which is at 50 C. We're in winter now and the room was at 19 C, so it's running at 31 C above ambient. In the summer heatwaves it could reach 35 C + 31 C = 66 C.
While the recommended maximum is 85 C, those 66 C won't help achieve the goal of a lifespan that is counted in decades 🤔.
One way to reduce the regulator temperature is to use a more efficient one.
The regulator PCB I'm using is based on Aerosemi's MT3608. Measuring the incoming and outgoing current and voltage gives an efficiency of 86%, which is a very decent number for a switching regulator boosting from 5V to 18V.
Maybe by using some of the latest ICs the efficiency can be increased to ~92%, but I don't think this will be enough to solve the temperature problem 🤔.
New ceramic lampshade design. Apart from the fact that the piece deformed when drying and that I sawed and sanded it after firing, it turned out "acceptable".
I like the fit between the wooden rod and the ceramic. The thermal design got a little worse; it now works at 1 or 2 degrees warmer than before.
And what I liked least is that now the lamp head is very large in relation to the base 🤨. So I have to think about how to fix this 🤔.
There are days when you wake up feeling a bit like Jony Ive, except for the tolerances 😂🙈.
This is the base of the second prototype of the Portuaria I'm working on now. The change in shape is to give more visual weight to the base with respect to the ceramic screen, because in the previous prototype I didn't like how that relationship turned out.
Another change is that instead of the printed circuit board it has an aluminum plate to better dissipate the heat from the regulator. The goal is to create a product that lasts several decades in regular use, and the rule of thumb is that for every additional 10 C the useful life is reduced by half.
It's probably not the final shape of the base, I'm already thinking of a third prototype that needs less sanding! 🤧.
New LED holder design, now with connector so you can change the LED without having to use a soldering iron 😎.
I did it to be able to mount the Bridgelux V8s I'm using, with 3mm polycarbonate scraps I had around here.
The future plan is to migrate to the Bridgelux V6s, which have more standard measurements and can be used with TE's Z35 holders.
🧵 #PortuariaLamp #lamp #prototype #LED #holder #lighting #DIY
Portuaria 0.3!
- More angles! Square and rectangular rods add contrast; it's easier to align the holes and slots when making them; and they use the same eucalyptus wood as the base instead of Palo Blanco.
- Larger base surface. The idea was to give the base more visual weight in relation to the ceramic screen, turning the circle into a rounded square without modifying the width and length. But I think I went overboard and now it's too big 😂.
- Aluminum heatsink for the voltage regulator. This worked quite well, the temperature of the circuits dropped 10 C compared to the previous version.
- New LED holder with connector. This allows changing the LED without needing a soldering iron, increasing repairability 💪. Made of polycarbonate for now, but perhaps ceramic in future versions to reduce plastic parts to the minimum necessary.
Recalculating! I've been doing measurements of various parameters on the last prototype, and I'm less and less convinced that it's a good idea to run a 5 watt lamp from a 5 volt USB 🤨.
Here's the list of problematic issues:
- Crappy USB cables 👀. Unless they're of very good quality, they use very thin conductors and connectors with dubious plating. This produces a significant voltage loss of up to 0.4 volts with the currents that the circuit handles.
- USB chargers. Usually you can only use up to half of the maximum current without the output voltage dropping too much.
- The voltage regulator I'm using loses efficiency if the voltage drops below 5 volts, and it gets too hot 🥵.
- The total efficiency is terrible, it only reaches 63% due to all the power losses from the previous points 😱. The Huanacus I built before with a simpler circuit that was only an 18 volt transformer, an LED and resistors reached 80% efficiency 😐.
But don't panic! 😁 I have a plan: Use a step-down LED driver like the one in the photo, with a switching transformer from 18 to 30 volts... or 20 volts from an USB-PD 😎.
The first tests gave a total efficiency of 87%, an amazing improvement 🤩. There are still some issues with the flickering produced by the LED driver (a whole topic, it's for another post), but they are being resolved 💪.
🧵 #PortuariaLamp #LED #driver #efficiency #flicker #electronics #USB
The design of the dimmable version of the Portuaria is progressing, slowly but it is progressing 🥳.
Organizing the wiring of the components inside the base was quite a challenge because there are things with fixed positions (potentiometer, LED cable, vertical rod and power plug) and the circuits have to fit into the gaps between those things 🤯. I think it could be simplified more, but for now everything fits into its place.
🧵 #PortuariaLamp #lamp #prototype #LED #driver #dimmer #electronics
I also managed to stabilize the driver circuit to reduce the oscillations of the light intensity to less than 0.2% (2 mV, 0.84 lumens), from 72% that the original circuit had 😱. The trick was to add four 22 uF ceramic capacitors in parallel to the LED, and another 10 uF at the potentiometer input.
The goal remains to simulate natural lighting as best as possible, and after all, the sun does not flicker 🤔.
🧵 #PortuariaLamp #lamp #prototype #LED #driver #dimmer #flicker #electronics
New electronics design that improves energy efficiency from 63% in the previous USB version to 79% with a new circuit that uses USB PD at 20V 😎.
🧵 #PortuariaLamp #lamp #prototype #LED #driver #USB #PD #electronics #efficiency
The problem with the previous circuit, which worked with the 5V of the common USB, is that it had a lot of power losses due to the inefficiency of working at such a low voltage. The charger got very hot due to the low conversion efficiency from 220V to 5V, power was lost in the cable due to the 1.4A current, and the step-up worked hard if the voltage dropped much below 5V due to using a charger or cable of dubious quality 👀.
The solution? Use the new USB PD chargers, which can deliver different voltages if we ask them nicely 😁. I'm using a board with the HUSB238 to ask the charger to give me 20V, which is enough to turn on the 17V LED and makes everything work more efficient and cooler because the current in the cable is only 0.25A, converting from 220V to 20V is more efficient, and the step-down to regulate the LED current is more efficient than the step-up of the previous version.
But not everything is pure pleasure in the world of USB PD. The USB PD charger I'm using is not a big deal, and has a standby power consumption of 0.125W when it's working at 5V (unpresentable for 2024 🙈), but when it's put to work at 20V the standby consumption goes to 1W! 😱. A 5W lamp that consumes 1W when turned off?!?! 💩
After a couple of days pondering this depressing result, I thought of trying something: Make the charger go back to 5V when the lamp is off!
The first attempt with the IP2721 chip didn't work because that chip can't renegotiate another voltage after power on, but I found another chip that can do it: the HUSB238! 🥳
The trick was to put a double switch and another cable to the HUSB238 so that when turning off the lamp it asks the charger to go down to 5V, and the result was quite interesting: 0.19W in standby, 80% less than before 💪.
More efficient USB PD chargers with GaN chips are already on the way...
John Foley@francc just took a scroll through your thread - not sure if I'm more impressed by your project, or documentation of it 😆
Nice work!