Big HEPA unit teardown

The PDL310 can be turned into a DL420 with a little jiggery. You gain a high current L-N test. IMHO the replacements with rotary switch are much nicer to use. The PDL310 "Hamal" label would crack and the buttons would go. Also the LCD design was by moi. Then I told the client to take it seriously and he never looked back. There are some things I should not do.

Mike Page

Active Carbon is (or was) used in gasmasks, so it removes more than just bad odors.

Zeedijk Mike

I do indeed have a PDL310 (and its sibling the PDRC380). And a SOK36 with capacitive sensing too.

Big Clive

Mine are capacitive. But I use a CMOS opamp. Like a voltstick, really. If you have a PDL310 or DL420 you have it.

Mike Page

I probably still have the hideously unpleasant prototype touch controller I designed decades ago, that used a microcontroller with directly exposed main referenced touch pads. I had issues with the input impedance and bias resistors meaning you could really feel the tingle when you touched the pads while grounded. It might be worth revisiting to see if capacitive coupling would work with a modern microcontroller.

Big Clive

You don't generally get that many comparators on a chip. But if you have that many comparator inputs you could switch around the pin functions in real time. I'm not sure it solves the problem; but generally analogue pins are better specced for leakage than straight digital. In fact the pins on my preferred small target - LPC824 - are specced 10nA. But I wanted some positive feedback to set a threshold. So I had an external SOT23 OR gate, and that was specced 1uA. I just wanted too much, didn't I? At some point I had to draw a line and do what works. I've not used the "touch switch" microcontrollers (eg LPC845 and Microchip have a bunch of them) but I think they work on mutual capacitance. They don't need the chip elevated to Live.

Mike Page

It's very cool. Means the software just has to create a simple square wave, and gets a high resolution volume fade for the ping noise.

Big Clive

I'm wondering if they were using comparator inputs to detect a lower voltage differential. Or maybe the chip does have touch input circuitry. As well as the usual supply decoupling capacitor there was one other one connected to a pin, hinting at an internal regulator or reference voltage.

Big Clive

After I rebuilt this unit I did actually put it in the same room as the 3D printer. Not sure if it's needed. I use PLA for almost everything which I think may be low risk.

Big Clive

That piezo - oh it's envelope modulation! You can do things with PWM duty cycle but it's a lot more work and changes the harmonic distribution. This is neat.

Mike Page

I'm intrigued by the touch switches. I use something similar on my testers as an earth reference - but this (^^^) is minimal. I had hoped to use something similar as a simple switch but there's a snag: if the capacitive current isn't enough to overcome gate leakage, you'll never get a transition. Accurate leakage specs are notoriously hard to come by. They usually say 1uA over temperature and you only have 50nA or so capacitive current. It might well work in real life, then you'll get a dirty board and it won't. I can't charge money for something that works by luck. So I end up over-engineering it.

Mike Page

Hi Clive, what are your thoughts on HEPA filter for 3D Printing? YouTube is awash with "solutions" . . .is there actually a problem? I have mt Prusa Mini+ in an enclosure, print daily next to my work bench. On warmer days (I'm in Oz so that is often ;-) I do sense the plastic and occasionally on large prints feel some eye irritation. Like most things my intuition is that 'dose' is the main factor. I'd like to build an extraction system (mainly just an excuse to design and build), but am aware of so many fake filters I may not. Thoughts? Thnx for the great videos, you've even got me watching the streams now . . . in the background while I'm pottering in my garage/workbench . . . it's like the random mate that pops in for a chat while you are trying to concentrate . . . except with your streams I don't feel guilty ;-) Thnx - Billd

Bill Donnelly

An Oxidise Karens machine is definitely the future! The figuring out of that pinger circuitry was a masterpiece of detective work! I’d never have got that one from what you could see there. My hat is off to you sir!!

Dave Roberts

It is literally the machine that goes ping.

Big Clive

Damn, was expecting a teardown of a High Energy Particle Accelerator ;)

Had a look for that component you couldn't find a datasheet for. First go there was nothing but then changed the 'o' to a '0' (LN8K05) and found it on alldatasheetdotcom

NN Thomas

I haven't even watched this yet, but I had to be the first one to write "Ah! I see you have the machine that goes PING!"

Stephen King

“Double Death ☠️ Beam” Capacitors! 🤣🤣 Love it, Clive 😜

Photon Phil

Love the "Oxidise Karens and Destroy Moon"

TopEndSpoonie