Review: Bedtime Bulb E27 LED (2200K, CRI95)

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maukka
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Review: Bedtime Bulb E27 LED (2200K, CRI95)

Bedtime Bulb sent me their warm LED bulb for testing.
Manufacturer website: https://bedtimebulb.com/
Store link: https://www.amazon.co.uk/Bedtime-Bulb-Low-Blue-Light-Healthy/dp/B07XWCNCDJ

The main specs by the manufacturer:
-CRI 95
-450 lumens
-6W power rating
-AC voltage range of 220-240V, also available in 120V
-2200K color temperature
-Dimmable with some dimmers
-25000 hour lifetime
-50000 cycle lifetime
-Indoor use only
-5 year warranty

Measurements

Measurements were made in a 50cm integrating sphere with an x-rite i1pro spectrometer after the bulbs had warmed up for 1 hour. Intensity (lux at 1 meter, candela) was measured outside the sphere at 50cm.

The bulbs were connected to mains power which at the time of testing was at 229V.

Output at 1 hour is 439 lumens. This is very close to the manufacturer’s spec of 450 lumens. The output is highly dependent on the input voltage though.

Power consumption was measured at 4.9 watts at 239 volts, but at another time 4.3 watts at 223 volts. Efficiency is ok for a very warm and high CRI light source at 90 lumens per watt.

For all practical purposes maximum output is reached immediately. Light output in lumens was plotted over one hour. The output doesn’t sag during warmup, but does vary a lot depending on the AC mains voltage.

That variation in output is visible to the eye. The bulb’s output is also very sensitive to electrical noise.

Color rendering

The CRI data was measured integrated after a 1 hour warm-up in an integrating sphere.

Sample #1

Sample #2

Color rendering is good reaching CRI Ra of 96 and R9 of 76. TM-30-18 fidelity index Rf of 94 and gamut index Rg of 101 are also excellent. Typical LED technology is evident from the minimal blue hump at 450nm, but as the color temperature is very low, there’s no dip at cyan wavelengths. Visually the light is very pleasing with a slight rosy tint to its very warm temperature of 2250K.

The two bulbs I tested were very well matched and should’t have any visual differences when installed in the same space. The manufacturer specifies the LEDs to be matched within MacAdam Ellipse of 1, which is very tight and totally invisible to the human eye.

Load IES TM-30-18 Color Rendition Reports by clicking the thumbnails:

CGATS CRI Data files:
Bulb 1: https://pastebin.com/6uqXtuXZ
Bulb 2: https://pastebin.com/TAuqRjj6

Color temperature and tint

Tint is slightly below the black body line on both bulbs. Remember that when LEDs heat up, their duv value almost always decreases and becomes less green/yellow. This was measured after 1 hour in an integrating sphere.

Tint shift is basically non-existent. Intensity increases ~70% when the light is measured from the side of the bulb, since the LEDs are positioned almost vertically inside the diffuser.

Flicker

The 100 hertz oscillation shown in the graph doesn’t cause any issues. The small modulation depth and a snob index of 0% guarantees that it’s easy on the eyes. The light is not suitable for videoraphy though since the flicker will be visible on higher shutter speeds. Please note that the output is not visually stable even though there’s no inherent mains frequency related flicker. See below.

I don’t usually notice any problems with LED bulbs when run from the wall at my house, but with the Bedtime Bulb there was continuous visible output changes. When used for indirect lighting, it didn’t normally bother me, but when looking at a surface lit by the bulb it was very noticeable. The light is marketed for reading, but unless your wall AC is perfect it isn’t suitable for that purpose. I have no idea if the 120V version fares better in this regard, but the 230V version needs better filtering.

Here’s three plots visualizing the light output over time from an oscilloscope with different power sources over 24 seconds. The measurement was setup so that the inherent but visually invisible 100Hz flicker didn’t show up.

AC voltage from the wall. There’s some visible change in output every once in a while.

AC voltage from a pure sine wave inverter with a lot of high frequency noise (Omni Ultimate). The light output has very visible and irritating flickering.

AC voltage from a simulated/stepped sine wave inverter with stable output (Omnicharge). The output is perfectly flat.

AC power draw

Current is drawn in short pulses 100 times a second as the input voltage gets high. There’s a hint of power factor correction which results in the current waveform vaguely resembling a sinewave. The power factor varied from 0.77 to 0.82 during testing.

Cyan line: mains line voltage
Yellow line: current draw of the bulb
Violet line: power draw (voltage * current)

Verdict
The Bedtime Bulb is a very warm and cozy light with beautiful tint and very good color rendering. As advertised there practically no blue light to affect your hormone levels at night.

The only drawback I experienced was the poor filtering on the driver. The output is very sensitive to AC line noise and changes in voltage. Changes in output were clearly visible in my testing from a wall outlet or noisy inverter but not when using a clean simulated sine wave from an inverter. For this reason I’m not sure I can recommend these. I haven’t tested the 120V US version and can’t comment on those.

Please note that the test was done when the bulb was brand new. I can’t guarantee that they will perform similarly after months or years of use.

Edited by: maukka on 02/10/2020 - 03:50
hank
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Color temperature isn’t a measure of the emission spectrum, it’s a measure of appearance to human vision.
What’s the driving emission of the underlying LED, likely to be blue or violet, and how much of that leaks out?

Can you check the spectrum? Spectrometers are cheap and easy to get nowadays:
https://i.publiclab.org/wiki/spectrometry

SunLike
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Nice =) I hope I will have LEDs from SmareEcoLightning with the same spectrum (1000pcs 6w 13.5mm)
I ordered it, because I understood bedtimebulb’s philosophy.

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yeutterg
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Hey everyone, Greg Yeutter here. Bedtime Bulb is my product.

Maukka, thank you for reaching out and for this awesome review. It's great to connect with a community that appreciates specs like high CRI and low flicker.

 

Product Availability

Regarding the product, we currently sell in the US and Canada (A19 and B10 versions).

UK is launching next week, with the rest of Europe coming in the following weeks. The European product is an A19 with either an E27 base or B22 base. As Maukka linked, the E27 version is already available for sale on all the Amazon Europe sites (except NL) but we are still finalizing the graphic designs. Expect the B22 version to be live by Monday.

 

Brightness Fluctuations

Regarding the brightness fluctuations, we've only seen it happen in the US on places with very noisy power (very unstable voltage). Perhaps this is more common in Europe? We always offer a full refund upon return to anyone who experiences this issue, or if they don't like the product in general. I appreciate the feedback on this, and we will monitor the situation in Europe to see if driver changes are needed.

 

Pump/Phosphor Design

hank, the current LED design is a blue (450 nm) pump with a special phosphor design that reduces most of the blue, while still providing excellent color metrics. We are considering violet designs for the future, but in general, these have less phosphor stability and will degrade much more quickly than blue pump designs.

I'm not 100% sure what you mean by "how much blue leaks out." Mauri captured the specs well with his spectrophometer, but we also have similar metrics posted on our spec sheet. Let me know if I can clarify anything here.

 

Thanks everyone,

Greg

Bedtime Bulb: The Light Bulb for Healthy Sleep

Lightbringer
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Hmm, looks interesting…

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hank
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Quote:
“how much blue leaks out.”

I mean, how big is the blue spike in a spectrum, like this:

I like the PublicLabs kit spectrometers, highly affordable.

Thanks for the info and the comment about the violet-driven LEDs, that was news to me.

OH, WAIT, I just looked at your web page and found the answer:

yeutterg
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Here’s an SPD on its own if that’s helpful:

Bedtime Bulb: The Light Bulb for Healthy Sleep

puglife2
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yeutterg wrote:

Hey everyone, Greg Yeutter here. Bedtime Bulb is my product.

Hey! I just want to know, on amazon.ca it’s $25 for your bulb and for $2 less I can buy a 6 pack of 2200K led edison light bulbs, maybe I missed something but what does your bulb do better than this 6 pack for justifying this price tag

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Note: I’m genuinely not trying to be snarky with this post. Just asking you to consider a different perspective, whether you like my product or not.

Do the 6-pack 2200K bulbs have good color performance or are they just 80-ish CRI? What about flicker? Shading of the bare filaments to reduce glare? And the elimination of “shadowing” where a pattern is projected on the wall? All issues with many filament products that we’ve worked out.

Some people will care and some will not, but I can tell you that just the LEDs in our bulb cost more than many light bulbs retail for. Custom phosphors aren’t cheap. But we’ve found a niche and many thousands of customers can attest that we’ve come up with something helpful.

Also consider that it’s my full-time job to educate people about human-centric lighting. I’m able to listen to what people are saying and genuinely try to find solutions for them. If we were making a smaller per-unit profit, I wouldn’t be able to do this. (By the way, I’m not rich. It took a lot of pain, debt, and suffering to get this business to a relatively stable place)

A comment on cheap LED bulbs: obviously they are great for the consumer in many ways. But it’s very hard to innovate when your per-unit profit is a few pennies. There’s a reason the big names are spinning out their consumer lighting divisions. Corners are cut on cheap products, many times on important things like flicker and safety certifications. Not always, but buyer beware that many things are misrepresented on Amazon.

I totally get it. The title of this forum starts with “budget.” You’re focused on value, and my product probably doesn’t fit that definition for you. That’s 100% fine by me. But if there is a product that fits your needs from a company that genuinely cares (instead of a commodity operation) consider supporting them.

Bedtime Bulb: The Light Bulb for Healthy Sleep

EasyB
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hank wrote:
Quote:
“how much blue leaks out.”

I mean, how big is the blue spike in a spectrum, like this:

I like the PublicLabs kit spectrometers, highly affordable.

Thanks for the info and the comment about the violet-driven LEDs, that was news to me.

OH, WAIT, I just looked at your web page and found the answer:

!{width:35%}https://images.squarespace-cdn.com/content/v1/59c9469ae5dd5bc276433d46/1...!


It looks like the measured spectrum is also in maukka’s info-graphs, at the top center.
puglife2
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Nice reply yeutterg, I ordered two to try it Thumbs Up

yeutterg
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Thanks for your support, and I’d love to hear your honest feedback. Cheers.

Greg

Bedtime Bulb: The Light Bulb for Healthy Sleep

maukka
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yeutterg wrote:

Regarding the brightness fluctuations, we’ve only seen it happen in the US on places with very noisy power (very unstable voltage). Perhaps this is more common in Europe? We always offer a full refund upon return to anyone who experiences this issue, or if they don’t like the product in general. I appreciate the feedback on this, and we will monitor the situation in Europe to see if driver changes are needed.

Just to satisfy my curiosity, I did some tests on the AC line in my house. I don’t have any expensive power quality measurements devices, but I used whatever I had on hand.

Checking my UPS logs, I can see that during the last couple of days the AC voltage has ranged from 218 to 230 volts.

First I measured the AC voltage vs. lumen output over 10 minutes. To me the voltage fluctuations don’t seem that bad (226.1V to 228.4V).

A typical constant current controlled bulb doesn’t react to these little voltage changes in any way and would look like this:

I tested the stability of the AC waveform at my house using the pass/fail function of my scope and making a mask around the waveform. I let it run for some time, but there was no sudden spikes all the while I experienced some visual fluctuations on the bulb. AC voltage ranged from 213V to 215V during this test.

And as can be seen from the scope screenshot, the waveform is quite clean. The THD of the AC line at my house is only about 2%.

And for testing the crest factor, I used a Uni-T DMM which can show the max/min values of an AC waveform in addition to the RMS value. With a perfect sinewave the ratio between those two or the crest factor should be sqrt(2) or about 1.41.

What I got was pretty much spot on (316V/226.2V=1.4).

I also turned off most SMPS power supplies and lights, but that didn’t make any difference to the behavior of the bulb.

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Too often testing the tests takes more effort than doing the tests themselves. Thumbs Up

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yeutterg wrote:
Note: I’m genuinely not trying to be snarky with this post. Just asking you to consider a different perspective, whether you like my product or not.

Do the 6-pack 2200K bulbs have good color performance or are they just 80-ish CRI? What about flicker? Shading of the bare filaments to reduce glare? And the elimination of “shadowing” where a pattern is projected on the wall? All issues with many filament products that we’ve worked out.

Some people will care and some will not, but I can tell you that just the LEDs in our bulb cost more than many light bulbs retail for. Custom phosphors aren’t cheap. But we’ve found a niche and many thousands of customers can attest that we’ve come up with something helpful.

Also consider that it’s my full-time job to educate people about human-centric lighting. I’m able to listen to what people are saying and genuinely try to find solutions for them. If we were making a smaller per-unit profit, I wouldn’t be able to do this. (By the way, I’m not rich. It took a lot of pain, debt, and suffering to get this business to a relatively stable place)

A comment on cheap LED bulbs: obviously they are great for the consumer in many ways. But it’s very hard to innovate when your per-unit profit is a few pennies. There’s a reason the big names are spinning out their consumer lighting divisions. Corners are cut on cheap products, many times on important things like flicker and safety certifications. Not always, but buyer beware that many things are misrepresented on Amazon.

I totally get it. The title of this forum starts with “budget.” You’re focused on value, and my product probably doesn’t fit that definition for you. That’s 100% fine by me. But if there is a product that fits your needs from a company that genuinely cares (instead of a commodity operation) consider supporting them.


I tell my customers (I am an A/V dealer) constantly that LEDs are THE place to invest. If you amortize the cost of a quality lamp ($25 per) over the life of the bulb (lets be super conservative and say 10 years) you’re looking at roughly $.20 per month per bulb.

I understand it’s a lot to lay out up front but you’ll be paying for cheap products (in the form of headaches and poor color rendering) for the life of the inferior product, which with LED technology is a long time.

That’s the problem with poor quality LEDs, you’re stuck with them for much longer.

I’m curious to check out a couple for our nightstand lamps.

hank
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Quote:
the LEDs in our bulb cost more than many light bulbs retail for. Custom phosphors aren’t cheap.

I’d like to try using your emitter in a flashlight (right now we use amber emitters in our evening flashlights).

Would you sell the emitter on a 16mm or 20mm board for hobbyist use?

yeutterg
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Watermanchris: 100% agree. Plus we have a 5-year warranty, so if the product does fail for whatever reason, it’s pretty easy to get a replacement out of us Smile

hank: It’s actually a filament operating around 70 V, but we unfortunately don’t sell them. We have a pretty tightly integrated supply chain. You may consider breaking open a bulb and using the filaments from there, but consider using cheaper filament bulbs first to test as they are quite delicate Smile

Bedtime Bulb: The Light Bulb for Healthy Sleep

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Greg Yeutter , Can I become your dealer?

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yeutterg
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Please send a private message here: https://bedtimebulb.com/contact

Thanks!

Bedtime Bulb: The Light Bulb for Healthy Sleep

hank
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Quote:
filament
Quote:
special phosphor design that reduces most of the blue, while still providing excellent color metrics.

Actually it would be the custom phosphor I’d like to get hold of.
I could dissolve it, I guess, and paint it over a blue or royal blue LED?

If you’ve patented the phosphor, what’s the patent number?

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Ah I see. Patent still pending. Right now, it’s going to be difficult to pull out of the supply chain, but we will reconsider for the future.

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maukka wrote:
the output is not visually stable … I don’t usually notice any problems with LED bulbs when run from the wall at my house, but with the Bedtime Bulb there was continuous visible output changes.

thank you for letting me know that even with stable power in Finland, the lights have visible flicker

I hope the manufacturer fixes the problem

yeutterg wrote:
Regarding the brightness fluctuations, we’ve only seen it happen in the US on places with very noisy power (very unstable voltage).

well… I dont mean to be snarky
however, you dont seem to have understood maukkas comments.

I suggest you re-read maukkas posts, and let us know when you have fixed your driver

clearly the problem with flicker is not limited to USA, nor to “very unstable voltage”

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Okay, so if I’m reading all this correctly, they’re phosphor-coated filaments?

Filaments have plenty of thermal inertia that only rather drastic fluctuations should be noticeable. The driver must exhibit some pretty serious fluctuations/dropouts to visibly register. Yeah, I’d say definitely work on that.

People used to grex about “pre-flash” when flicking on moonlight/firefly mode on some lights. Having visible stutter on a lightbulb would be a pretty serious glitch.

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yeutterg
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@jon_slider It’s unclear why you think I don’t understand this discussion. I can confirm that this is a very rare issue with the US bulbs. We’ve sold 10s of thousands with mostly happy customers. Like I said, we only see visible changes in places with power that’s too noisy.

Maukka was literally the first person to test the first batch we ever shipped to Europe. It’s good to know upfront if we have a potential issue with this batch.

We will keep testing to see if it’s an isolated case or a widespread case with the European version. The prototype did not have this issue, so we are doing an investigation to see what changed from test to production.

@Lightbringer They are LED “filaments.” Similar concept to regular discrete LEDs except shaped differently, plus our custom phosphor. The stability of light output is mostly due to the driver circuit as the diodes themselves can fluctuate very rapidly to changes in input.

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yeutterg
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Europeans (EU countries + UK only): interested in helping me do a test of my bulb? I’ll send you a free Bedtime Bulb if you don’t mind helping me out with a small experiment.

I want to see if the issue that Maukka had is replicable in other regions of Europe. All I would need you to do is to screw in the bulb, observe it for a few minutes, and see if the light is constant or not. You’re free to do whatever you want with the bulb after the test.

If you are interested, please send me a private message with your name and shipping address. Also specify if you prefer the B22 Bayonet base instead of the E27 screw.

E27 Screw version: https://www.amazon.co.uk/dp/B07XWCNCDJ
B22 Bayonet version: https://www.amazon.co.uk/dp/B07XW7NHQT

Thanks,
Greg

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yeutterg wrote:
@Lightbringer They are LED “filaments.” Similar concept to regular discrete LEDs except shaped differently, plus our custom phosphor. The stability of light output is mostly due to the driver circuit as the diodes themselves can fluctuate very rapidly to changes in input.

Okay, so when you say “filament” it’s more a form-factor (similar to COB LEDs but on a string vs on a board), and not a heated filament as in incandescent bulbs.

I was curious what kind of phosphor would be thermally excited to produce light… that’s what threw me by use of the term “filament”.

So it would in fact be subject to flicker, etc., if the driver passed through voltage variations (hiccoughs) in the mains supply.

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Yep, depending on how well the driver handles variations in the mains Smile

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yeutterg wrote:
Watermanchris: 100% agree. Plus we have a 5-year warranty, so if the product does fail for whatever reason, it’s pretty easy to get a replacement out of us Smile

hank: It’s actually a filament operating around 70 V, but we unfortunately don’t sell them. We have a pretty tightly integrated supply chain. You may consider breaking open a bulb and using the filaments from there, but consider using cheaper filament bulbs first to test as they are quite delicate Smile

Where could us fun loving folk buy some LED Phosphors in small quantity? Do you know any good sources?

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https://duckduckgo.com/?q=led+phosphor+%22sale%22
finds a bunch of suppliers and some information about which phosphors have what color output.
E.g.:

Quote:
Our LED phosphors provide unprecedented blue light down selection access to the entire color spectrum, regardless of the manufacturer of the underlying blue LED chip. Our innovative materials provide uniform light output at the desired CRI and CCT, without being impacted by the variations in light output from chip to chip or from manufacturer to manufacturer. With our fully patent-backed solutions, we provide unparalleled expertise in our industry leading support.

Learn more about Intematix’s Phospor Materials for LED Lighting …

. [link on original page]

Hmmm, I can imagine BLF getting into custom mixed phosphor creation.
Here’s the tech note page on blending phosphors: http://www.intematix.com/uploads/application%20notes/PhosphorBlendingApp...

Find a source of the “underling blue LED chip” and start mixing up phosphors.

I recall when the original single-phosphor “office white” fluorescents got driven out by “triple phosphor” high color rendering fluorescent tubes.
Triple phosphor lamps had another advantage, as some phosphors have a long decay time so kept puttiing out light when the AC power 60 cycle went through its zero point or the AC power flickered briefly.

Yeah, I’m a dinosaur.

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Not aware of any consumer-level retailers. Maybe talk to Yuji. They can do some low-volume LED finished goods and they mix custom phosphors. Perhaps they could sell the phosphors but I can’t guarantee it.

Even a few grams can be pretty pricey though. A little goes a long way!

This is a cool page just to learn about the contribution of various phosphor materials: https://www.yujiintl.com/phosphor.html

Bedtime Bulb: The Light Bulb for Healthy Sleep

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