In this video I used a Keithley DMM6500 bench multimeter in diode mode, unlike a typical handheld multimeter it has a relatively high diode test voltage of 7 to 12 V and can do higher test currents. But you can do the same test with a lab PSU at a similar voltage (>6V for those 3 die LEDs) in constant current mode set to just a couple of milliamperes, just be careful of the PSU's output capacitance damaging the LEDs if you set the voltage too high, adding a resistor will help prevent that.

That's a good point. Unfortunately I don't remember where I got that number from. I can only assume I misread the datasheet's 0.1 L volume as a flow rate of 0.1 L/min as that seems suspiciously low considering a typical 20 mm blower fan like that can do 50 L/min, although they're not running it at full speed in this sensor the fan couldn't operate at 0.2%, it would stall before then. Taking a complete guess I would say somewhere around 10 L/min is a more reasonable flow rate to expect.

You might be able to carefully insert a thin pry tool between the lens and outer shell and then push it back and forth getting deeper every so often to try and cut any silicone adhesive, gentle heat may also help. Although you might find the lens is glued on with a stronger glue or ultrasonically welded which makes opening them without damage impossible.

Some things that give it away it's an inductor: - PCB silkscreen has it marked as "L1" ("L" in honor of the physicist Heinrich Lenz) and an inductor symbol between the pins (easiest way to know it's an inductor) - Axial through hole inductors are often that light blue colour and are much wider than resistors with a slightly lumpy mid-section - The colour bands decode to 3 mH which is a relatively large inductance value, but makes sense in the circuit (if it were a resistor it would be 3k Ohms 10% which would limit the current too much and dissipate about 1.5 W of the 5.5 W of this LED bulb) - It would measure almost 0 ohms but about 3 mH on an LCR meter (if it wasn't broken) - The cross section shows it has a ferrite core and low resistance copper wire wound around it, a wire wound resistor would use a nichrome alloy wire wound around a ceramic core.

Tim thanks for taking the time to put up the video , i have next model onwards , the same component on my board was defective and the capacitor near it , top looked to be swollen , i changed them both out and we are back in action , machine working again . cheers

Side note: I'm very familiar with the 12s internal workings, if you have any questions about the workings of your unit I'd be more than happy to help. I'd also recommend giving the service manual a thorough read, it's freely available online and whichever version you find will likely apply just fine

Interesting! I knew about the dump circuit and have heard it be switched in when you command a charge but then cancel it, but didn't know it could be switched in during the discharge but now I think about it, it makes sense it should. I have had a couple instances discharging into strange loads often with bad contact it gives the "ABNORMAL ENERGY DELIVERY" or "ENERGY NOT DELIVERED" messages, but can't remember what sound it made. Unfortunately I didn't record the screen of the LP12 but I did have another wide camera angle I used for the audio which happened to record the therapy cables jump a little from the magnetic field during the discharges and I can hear the 3 beeps after for the priority 3 tone so I think it probably did get the full or part of the 360 J. The _thud_ sound in the recording does sound different to the usual _click_ of discharging into 50 ohms, I can't remember what I did for the audio, I might have recorded it with a lapel mic, possibly very close to the LP12, but I can see in the edit I put a +24 dB gain on it otherwise you can't hear it, in the raw recording it's a very quiet _click_ sound. Next time I'll also record the discharge waveform with an oscilloscope current clamp and HV probe so I can show the real peak power the component is subjected to (18.5 kW figure is just for 50 ohms) and be confident it actually discharged properly in both phases. And thanks for the tips. I certainly would not be using it without having first read the operators manual and service manual (which are really good). This particular LP12 was damaged in shipping from it's annual calibration so was written off as a total loss, I got it and replaced the shattered LCD and repaired the ECG/SpO2 PCB. I've been meaning to make a video about the whole thing but haven't had the time. But I will eventually! And thanks for watching! I remember when I got the LP12 I watched quite a few videos about them including yours so cool to see you here.

@@WizardTim That's cool! I didn't know you came across those old vids. I also recently fixed up my 12 and got it calibrated and repaired and the software updated so it's just like new and made some new vids on it. And you'd be right in thinking some energy would make it even with an abnormal delivery message. I was messing around one time and zapped an apple, made a big spark along with the abnormal energy delivery message. Im more familiar with how the defibrillator reacts with hard paddles since it's more lenient on letting you discharge those into thin air or strange loads (where most of the time it'll just engage the dump relay). I'm more hesitant with using the therapy cable for experimenting because I want to keep it in good shape in case someone licks a power outlet wrong but luckily I have a couple of other units with cable that I can experiment with (though they are monophasic). If you want I can invite you to a small little med tech enthusiast discord I run, we have a good number of people who are knowledgeable in different tech for example I am the resident expert on LPs while another person knows more about Zolls. All the best!

Hmmm, it could be a lot of things so unfortunately I can only give you a couple pointers of what to investigate, could be: - 5 V supply is low, it needs a solid 5.0 V, it won't work properly at for example 4.6 V - 5 V supply could be noisy and causing interference, likely if you have other power electronics sharing the same 5 V or maybe a loose wire - A programming issue or noise on the TTL serial TX/RX lines possibly from a loose wire (I think there's a checksum in the packets it sends, not sure if most libraries check it's valid) - Dust on the internal photodiode (unlikely if you've just bought it)

Thanks! Hmm, I assume this is one you're using yourself with an Arduino or something? Typically when something doesn't work and just gets hot it's usually because it's electrically damaged which is what happened to mine at 3:09, I plugged it in backwards and instantly blew up that regulator IC. I'd double check it's the motor and not one of the ICs that's getting hot, also check the fan rotates by hand without power to check it's not mechanically jammed. Another thing I have noticed with them is they really need a good 5V supply, the 5 V pin on an Arduino or similar will often cause problems because they have a diode between the USB port VBUS and the 5 V header, check with a multimeter it's like >4.90 V and not something like 4.4 V (5 V minus a diode drop). Cheap thin breadboard jumper wires can also make poor connection or break internally so check them over as well.

Agreed, I even have a special bench-top multimeter than I can screen capture from, but completely forgot when recording this video to do that! In the new videos on this channel I have thankfully remembered (so far) to record the multimeter and put it in the video. The inductor smooths out the noise and voltage spikes on the AC mains to protect the LED circuit in the bulb but also prevent noise from the LED circuit going back out into the AC mains and interfering with other stuff in your house, it does this in combination with the capacitor, this is called an 'LC filter'. It does this by absorbing the voltage spikes in it's magnetic field. A resistor often used for a similar job in combination with a capacitor this is called a 'RC filter', but they have no magnetic field so instead convert energy into heat, thus it would get extremely hot and make the bulb very inefficient. It's often difficult to tell the difference between those axial inductors and resistors but typically you can tell based on the shape, inductors are usually shorter and wider than most resistors. Also ones like the brown one the coating is thin enough you can just make out the windings. In this example it's easier because there's a little inductor symbol on the PCB between the pins and it's labeled 'L1'.

​@@WizardTim Thanks a lot, that was a very good detailed explanation. I'm surprised how no video I have watched for the past week trying to learn electronics explained or even mentioned inductors. I even googled inductors vs resistance and I didn't get a clear answer or picture comparison. I just bought a new multimeter so I'm excited to try and test these components myself.

@@mhnoni Inductors aren't used anywhere near as much as resistors or capacitors so they're usually not taught until later in electronics. You'll probably understand it better if you think of inductors as the compliment to a capacitor rather than a resistor. - Capacitors try to smooth *voltage* by storing energy in their *electric field* - Inductors try to smooth *current* by storing energy in their *magnetic field* - Resistors *limit current* by dissipating energy as *heat* Also you'll find almost all multimeters can't measure inductance, usually you're measuring resistors, capacitors or diodes, you rarely need to measure the inductance of an inductor so they don't include that feature most of the time, in this video I was just measuring the resistance of the inductor to check it wasn't broken internally which of course it was broken. I have an LCR meter to precisely measure inductors, capacitors, resistors and all their characteristics, but you only really need that when designing more advanced circuits.

Unfortunately I don't remember the exact brand I used in this video, but it's at least not a UV resin. It's an "ultra clear deep cast epoxy resin" which comes in two parts, the advantage of this type is it isn't very viscous so it flows easy around the part and can be used in reasonably large moulds without overheating. The downside is the ratio of the two parts is very sensitive and it takes several hours to cure.

Bunnings has the "HPM VIVO PIR Sensor" (MPN: EV803PIRWE) which is a 'wall plate' style PIR sensor, however it doesn't have any manual/auto or on/off switches on it like the XL632. If you need the switches you might be able to get a 3 gang switch plate and use a Diginet LEDsmart+ PIR sensor (MPN: MMSE/PR) and transplant the old labeled switches. But I got mine replaced with just a standard PIR sensor and single light switch as it was less than half the price of any of the wall plate style sensors.

I did look at some very nice used Mitutoyo objectives but decided against it as both they were expensive but also they were all infinity corrected which would probably be more useful in future but would have required a separate expensive tube lens and more adapters. I ended up going with that cheap generic Chinese objective and instead spending my money on a telecentric lens from SPO which I didn't show but a photo taken with it is at 17:07. I also redid the thumbnail of PMS7003 video, it's now a stitched mosaic of several telecentric photos. Since this video I've ended up using the telecentric lens a lot more than the microscope objective so I'm not too sad about the microscope quality, although I do have a new tube for it which gets rid of that bloom in the center.

@@WizardTim Yeah that's true, seems like a great decision. I read a review of that 4x .10NA objective and when purchasing it I ended up buying many more objectives of the same style, I couldn't believe the price for $500 I got 6 plan objectives brand new so I wasn't expecting much for the other objectives but I took the risk anyway and well they were better than I expected however I feel like I "outgrew" them, first issue to me was the short working distance specially the 20x one and later the lack of epi-illumination, also recently I got the bug of photolithography and I think some mitutoyo objectives would be superb for all this. So now Im saving up to get one, hopefully two of them the 5x .14NA and the 10x .28NA The other models are way too expensive but will have an eye on the used market, with some luck I get a high NA objective for an affordable price.

Yes 100%, I see that regularly on PCBs in high end products and I've been tempted to do that with several PCBs, but ENIG is just such an expensive option when I'm only ordering 5 or 10 prototype PCBs (4-8x the price of a standard PCB) which is less cost effective than just adding a SMT heatsink, plus the gold is often only like 0.02 µm thick so you don't even get that vibrant gold finish :( I will add on the other hand aluminum core PCBs have really come down in price (only ~2x the price), I've had a play around with some designs using that and it's a massive performance increase, but the single sided limitation really limits the application, only used it so far for LED stuff.

@@WizardTim I wanted to say that copper or ENIG or HAL are all good for heat dissipation but not green solder mask on copper, which is as running with a pull-over. On your video, it seems that you have green solder mask on the dissipation aera ?

@@zianzan4536 Yes both the green and white PCBs have solder mask over the heat dissipating areas. I don't think I've ever done a PCB with an exposed area for a PCB heatsink that was HAL, I did try once with a silver immersion finish, was happy with it at first but it tarnished really quickly, so I might give HAL a try in future for PCB heatsinks. I've seen some PCB designs that expose strips of HAL in a PCB heatsink and the wave soldering process adds extra solder, I can imagine that massively improves in-plane thermal conductivity.

@@WizardTim :) I'm doing PCB for 20 years now, and yes : no vernish over dissipation aera. Yes : HAL is not a good finishing in that case of dissipation aera (unesthetic and solder is not uniform), but ENIG is perfect : more than 50 boards done with this finishing and with dissipating areas. With vernish : almost no dissipation is possible, it's not mettalic, it's as a cover. A nice trick with ENIG and a transistor with thermal pad SMD : let a litlle band of vernish between SMD pad and dissipation aera to avoid solder going on dissipation aera. I'm using a thermal camera too and I've strange results with ENIG dissipation aera : heat is not the same with angle of the camera (a hot spot of 60°C can be shown only on some angles, otherwise it can be 25°C and the hot spot is not visible), very strange, do you have same ?

@@zianzan4536 ENIG areas will appear as if the temperature changes with the angle of the camera because ENIG and most other metals have very low emissivity and high reflectance, so that 25°C is just the reflected room temperature. You can get around this by putting some Kapton tape over it which has a high emmissivity, but that will change the thermal performance.