Not sure if others would have interest in this, but I'm designing a PCB for an easy-to-solder TH node. As presently conceived, it would have 3 surface mount components (an LED on the front and a resistor and capacitor on the back), plus a DIP atmega328p, a header to accept an inexpensive si7021 TH breakout board, an FTDI header, and an RFM69HW. The idea is that it would run at 8Mhz and be powered by two AA batteries, so it's sized to be compact but still easy to solder. The same thing could be achieved with wires and some of the other boards out there, but this might be a little tidier if a TH mote is what you want as either the starting point or the end-point.

PCB dimensions are 0.65x2.55 inches. i.e. it is narrower than a typical AA battery holder, but roughly the same length.

The LED and resistor are optional, and you could forego the capacitor as well if you wanted a truly bare bones TH solution. However, the pads are there if you wanted to utilize them. Also, you could skip the si7021 BoB if you wanted just a generic mote.

I had hoped that someone would make an easy to solder board like this for the RFM69HW, but I got tired of waiting and finally decided to just make my own.

I found a good place to do range testing.... too bad I didn't bring the gear!

Good news! Last night I did some accelerated load testing on the supercap. First I charged it to 3.6v and then I hooked up an RFM69HW mote which woke up once a second to do 3 things: 1. check the voltage level, 2. turn on an LED for 1ms to simulate a sensor load, and 3. transmit a packet containing the voltage data using the RFM69HW.. Bottom line: 14,111 packets transmitted before running out of juice.

Not bad for a first attempt.

Yesterday received the PCB. Today assembled for testing this battery-powered nRF52-based passive infrared motion detector:

Made this 12 button keypad. Requires only one analog pin to read which button is pressed, and any button press can also wake an arduino from sleep:

Consumes no power when no button is pressed.

A pair of lithium AA primaries is hard to beat because:

1. Unlike alkaline's, they don't leak.
2. Have a look at the discharge curve: https://data.energizer.com/pdfs/l91.pdf By the time they drop to 2.4v, if not before, you'll want to replace them.
3. Obviously much longer life, both shelf life (20 years!) and energy capacity.

I think running 8Mhz from the internal RC is a no-brainer: wake up time is less than 4us. So, if your node wakes up often, you'll save a ton of energy over time.

The best time to take your battery measurement is immediately after a Tx. That will give you the most conservative reading. Save that measurement in a variable and then send it in your next transmission. Switch on your ADC just before Tx and take your first ADC measurement during Tx, because you have to throw out the first measurement anyway. That way you can take a fresh (and valid) ADC measurement just after Tx before the voltage rebounds.

Hope that helps!

Here's the version that I most recently assembled:

As you can see, the 15F supercap is now on the board itself. It works fine.

I've since made a few refinements and have sent the new files off to be fabbed. The newest version of the PCB will measure roughly 22mm x 22mm.

Put together this pro mini nRF24 shield for testing...

I have a number of sensor projects that sit within the nice footprint of a Pro Mini. Now I want to find a kind of universal power platform--hopefully small--to power them. So far, what I came up with was this, which runs the Pro Mini from 2xAAA batteries, and where the Pro Mini (and whatever the project built on it) simply "plugs in" to it:

Is there anything better? Ideas? Comments?

@robert022 Learn how to program in assembly language if you want a low level perspective. Lower than that you'll be building circuits!

Or, maybe something like this:
https://www.aliexpress.com/item/32653823271.html?spm=a2g0o.productlist.0.0.17ec6b694kraVc&algo_pvid=9be973d5-8868-4815-9e2c-75c046c6b849&algo_expid=9be973d5-8868-4815-9e2c-75c046c6b849-1&btsid=0b0a557016040910481015724e7c0e&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

which is 75v, still single phase, water cooled, but it has a recognizable ER8 on it. Costs around $175, delivered.

I'd probably opt to pay more, though, to get something with less runout, like maybe this:
https://www.aliexpress.com/item/4000812286377.html?spm=a2g0o.detail.1000060.2.97ea29d2lqjJXu&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.169870.0&scm_id=1007.13339.169870.0&scm-url=1007.13339.169870.0&pvid=dafeb530-8e0e-478a-8fdf-1fa3b2193609&_t=gps-id:pcDetailBottomMoreThisSeller,scm-url:1007.13339.169870.0,pvid:dafeb530-8e0e-478a-8fdf-1fa3b2193609,tpp_buckets:668%230%23131923%2328_668%23808%233772%23437_668%23888%233325%2317_668%234328%2319940%23948_668%232846%238115%23852_668%232717%237563%23559_668%231000022185%231000066059%230_668%233468%2315607%2336

which claims a runout of just 0.004mm, because whatever spindle runout there is will get amplified at the tip of any bit that gets inserted. I just have no way of knowing by how much it will get amplified, so for that reason I'd lean toward minimal spindle runout. They also claim to be the spindle manufacturer, so in theory they should know what they're talking about. Since the spindle itself is rated for only 75v, hopefully I could find a VFD somewhere that runs from 110v input voltage, which here is a lot more convenient, without having to wire for 220v or step 110v up to 220v just to meet the more typical Aliexpress VFD input requirement of 220v.

high speed 300W water cooled spindle motor 36000RPM 60000RPM 75V ER8 collet diameter 75mm milling spindle

$132.94

300w Spindle kits For Intricate Carvings Water Cooled Spindle ER8 60000rpm spindle motor 1000Hz water cooling & 1.5kw inverter

$286.06

So, with ER11 now abandoned, it opens the possibility to something like:
https://www.aliexpress.com/item/32837403762.html?spm=a2g0o.productlist.0.0.309b13aeeW38rW&algo_pvid=2ec935ea-2c66-44ff-90b5-31e667176b31&algo_expid=2ec935ea-2c66-44ff-90b5-31e667176b31-3&btsid=0bb0623c16040901544143852e25d3&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
which would be less than $200, delivered in just a couple weeks. It claims runout is 0.01-0.02mm (which sounds encouraging, though it doesn't indicate where the runout is measured from). It's 36v, allegedly single phase, which maybe means it could even be powered using a simple 36vdc power supply coupled with a PWM motor speed controller? For example, maybe this?
https://www.amazon.com/gp/product/B081YQW36Z/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

The collet itself looks a bit mysterious.

60000rpm Spindle Motor 95w Dia 48mm Natural cooling High Precision for CNC Engraving Milling Machine Permanent Torque

$161.92

WHDTS Signal Generator Motor Speed Regulator DC 5V 12V 24V 48V 500W 12A PWM Motor Driver Module LED Display High-Power DC Motor Speed Controller

$13.99

1 available

@executivul said in CNC PCB milling:

If I "tune" the position of a new endmill I can reach 60k rpm without any vibration at all, so I get almost no runout.

How do you tune the position of a new endmill? Are you referring to how far into the collet you are inserting it?

BTW, thank you very much for your posting. It was extremely helpful. I didn't know anyone was using ER8, but from your positive experience, it sounds like ER8 may be the way to go. All else being equal, it makes sense that a narrower ER8 assembly would be prone to less runout, as an imbalance on a wider ER11 assembly would obviously be amplified more at higher RPM's than an equivalent imbalance on an ER8 assembly.

If you don't mind my asking, which manufacturer and model ER8 60,000 RPM spindle do you have, and from where did you source it?

@ncollins Funny thing: when I look now at the photo for the 60000RPM ER11 spingle, the marking on the spindle itself shows only just 24000rpm. Similarly, the specs contradict themselves as well: the title says 60000rpm, but the speed (RPM/Minute) table shows 24000. It's this sort of inconsistency by Aliexpress sellers that gives me the heebie jeebies. For that reason, I'm guessing it's not really 60,000 rpm after all, which would explain why its price is considerably lower than the other 60,000 rpm spindles on Ali Express. If the Aliexpress seller were to send me a 24,000 rpm spindle instead of the 60,000 in the headline, I'm really not sure how that would play out for buyer protection, given the inconsistency portrayed in the description. I would try hard not to buy from a seller like this one, whose listing so badly mixes up the product data, as it seems like a heartache just waiting to happen.

@ncollins Sure. For example, an ER8:
https://www.aliexpress.com/item/32651625780.html?spm=a2g0o.cart.0.0.7a203c00aR74s0&mp=1

and an ER11:
https://www.aliexpress.com/item/32948530784.html?spm=a2g0o.cart.0.0.7a203c00aR74s0&mp=1

I tried to make it apples to apples. Prices are constantly fluctuating, so at the moment this particular ER11package seems priced lower than a lot of the other ER11 60,000 RPM packages, so that will contradict my earlier 2x statement (which is more of a running average across different vendors). At the moment, the price looks fairly attractive, if the quality is there. If the quality is poor, I'd probably be stuck with it, so there's a lot of risk in buying from sites that don't list the tolerances.

Marcos Reps suggests that buying used industrial equipment might be a safer path, because on his theory most industrial equipment gets replaced while it still has reasonable life left on it, and the quality tends to be high to begin with. But in his case, because of his vlogging, a manufacturer actually just gave him a high quality spindle, so he never really tested his theory.

Which 60,000 RPM spindle manufacturer is the best value? It may boil down to who makes it and what the tolerances are. That sort of info is often missing from the aliexpress listings. If the etchings on the spindle cases can be believed, then in this particular comparison the manufacturer is the same (namely, Changsheng).

Anyhow, Wegstr, for instance, seems to get great PCB results without relying on such massive spindles, so maybe I should be looking elsewhere.... But where, exactly?

Also, who makes the best VFD? I've read that certain brands are problematic, but I haven't kept a list (yet) of which ones to avoid.

These spindles are quite heavy, but maybe the extra weight would just amount to more preloading, which maybe (?) could be a good thing. I do like the portability of my CNC, which a Marco Reps style machine has clearly lost, despite its other advantages.

High speed 60000rpm CNC Milliing spindle motor 300w 75V Water cooled Spindle Motor + 1.5Kw AC220V Frequency VFD Inverter

$210.00

800W Spindle Motor kit 60000rpm Water-cooled Electric Motor Spindle+ 1.5KW VFD Inverter+ ER11 Collects+ 2M Cables for CNC Router

$181.34

I received useful guidance from the guys at uStepper:

1. They advise that I can go up in voltage, no problem--all the way to 42v if I want. Even at 42v there's still some safety headroom leftover. However, they advise against increasing the current, unless absolutely needed to avoid stalling, as that may lead to overheating, unless active cooling (a fan) were to be added.
2. "10mm/revolution a 32 microstepping input will give you 0.0016mm resolution. " This is a good point. Actually, with the current lead screws I'm at 8mm/revolution, and if I switch to ballscrews it will be either 4 or 5mm/revolution, which would be even better. Hence, maybe even the current (default) 16 microstepping is good enough.

So, I guess once I get limit switches installed, then before I get fancier it'll be time to do some milling and see if I notice any improvement brought by just the uStepper drivers alone. Then I may upgrade to the 20,000 RPM motor to see what, if any, difference that makes.

I still have my eye on a 60,000 RPM spindle. They seem not much more expensive than the 36,000 RPM spindles. I've found ER8 60,000 RPM spindles for less than $200 delivered, but ER8 seems like it would be too tight a fit (?), especially for regular router bits like the ones with 1 inch diameter heads used to flatten spoilboard. For some reason, ER11 60,000 RPM spindles seem to cost around twice as much, though I have no idea as to why. Is it really that much harder to make an ER11 spindle than an ER8 spindle that's otherwise the same?

Here's an example from the new Flume (version 2) water meter monitor:

It gets strapped to your water meter, typically in the ground. All it has is one gasket to seal out everything. This particular box just snaps closed. No screws! Quite a difference from Version 1, which also used a gasket, but had 12 screws holding it snug.

@sundberg84 Gaskets that are held under tight compression seem to work well at holding out moisture. I've seen a number of commercial products that rely on that and only that for in-ground radio sensors.

@ncollins Just wondering: why 4 load cells per sensor instead of only one?