HeaterMeter on the Raspberry Pi Model A+


 
Bryan Mayland

Bryan Mayland

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I was hoping to get to this this weekend but a bunch of stupid stuff happened so I had to put it off. I managed to get off at 5pm today (Thanksgiving Week Miracle) so I grabbed a kit off the shelf and soldered a HeaterMeter together in 45 minutes sans alarm circuit. A quick mating check confirmed my measurements that the A+ fits and I installed the remaining alarm compnents:
-- 1k resistor soldered to top instead of bottom of board
-- Q2 MOSFET soldered to top instead of bottom of board. Notice that it needs to be mirrored (flipped 180 degrees) to still have the correct polarity.
-- Installed piezo alarm at an angle so it didn't interfere with the A+'s 40 pin connector.




I didn't have time to print a case but I grabbed one of the scraps from the 4.2 case development and it fits just fine. The HDMI connector hits the printed support, but cut off ~1.5mm with a razor blade and there's no contact.


Note, the latest start.elf. startup.dat, fixup.dat, and bootcode.bin must be copied over the LinkMeter v12 firmware from the Hexxeh GitHib. Not sure if all of these are needed but I will investigate further later. EDIT: The latest OpenWrt LinkMeter firmware snapshot includes these.

The wifi adapter is inside the case but it doesn't seem to affect the range by any measurable amount. I don't know if I'll have a chance to update the wiki before Sunday, but looks like there is a viable alternative to the super overpriced Pi B now. Wifi comes up in AP mode, I just connected to it, then scanned and joined my home network. Rebooted and went to HeaterMeter Device Manager and it showed up about 30 seconds later.

NOTE: The Raspberry Pi A and A+ both seem so have USB compatibility issues with RT5370 which cause them to drop off after a while. Use rtl8192cu chipset wifi adapters!
 
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Actually all the supports are in awkward places. Because the pins don't start at the edge of the board any more, the SD card holder now goes under the board by about 7mm where it contacts some of the components there. The bottom support isn't on a blank area any more either, thanks to the extended header. The top one happens to be where the HDMI jack is so the difference between the jack extends off the board and the PCB needs to be accounted for.





If the supports could be changed to use the 4 corners that would be ideal. The bottom right one starts immediately to the right of where the the HeaterMeter RPi header ends. Easier to just remove the right SD card and bottom support probably though.
 
Have you given the B+ model any further consideration? Is it just the second USB header that conflicts with the power jack on the HM? (beside the extra pins on the header that you conquered on the A+ model). If you move the power connector to be snug next to the RJ45 port on the HM (and perhaps push the pair toward the edge of the board more if possible) might the HM and the B+ mate together?
 
I think about the B+ every few days and play around with layouts. Just shifting the connector down and having the power right against the blower RJ45 adds ~0.25" to the size of the board to make it fit. Ideally there should be some space between them too so you can actually access the connectors more easily. The overall device would be 8% bigger overall which is a pretty big step up. It is already at the threshold where I think it is too broad.

I'm also considering other options, like cube or more trapezoidal shapes or a box with a front panel...
 
I know the HM board got wider (side to side) on v4.2, how about making the board more narrow like previous versions and a little taller instead? That would make the overall HM shape (in the case) a bit more square instead of wider than tall as it is now. I kinda prefer the square or taller than wide design myself, because the connectors are all on the sides, so you need less space to set the HM when it is thinner....
 
how does this not have more responses, this is great news as the pi price just got cut in 1/2. very cool Bryan.
 
For the record, the A+ with wifi, HeaterMeter and LCD at 50% brightness averages 100mA at 12V. The regular B pulls 200mA at 12V. This means a standard UPS 12V battery can run an A+ Pi for about 15 hours vs about 11 hours for the Pi B.
 
I saw that Newark reported they had 86 RaspberryPi model Bs for sale so I tried to buy 75 of them to sell at cost with the HeaterMeter kits. They emailed me this morning
In regards to the above order, I’m afraid the Raspberry model you are looking for has been discontinued, the replacement is 68x0155. Please advise
Click to expand...

Welp, looks like Model Bs are done and I'm going to have to bite the bullet and go with a B+ design I'm not happy with (especially because A+ and B+ boards are no longer footprint compatible).
 
Because many prefer the ethernet jack and it is easier to modify something that fits the B+ to also fit the A+. I'm not 100% sold on the idea but if I designed for the A+ then the B+ would never be able to be used.
 
I was afraid the introduction of the B+ would bring the death of the B model even though it supposedly wasn't meant to. Even if it was still available the price of the B model is getting prohibitive and will force a move to the A+ or B+ model anyway.

I just ordered an A+ last night (for $25 including shipping from NewEgg), it seems the Amazon Prime price on the A+ is about $30 now... The current going rate for the B+ seems to be about $36, so were talking only $5-10 difference between the A+ and B+ models, that's not much... I can see an argument for both, the A+ using less power and allowing a smaller footprint at a cheaper price, while the B+ has more memory and USB ports and the onboard LAN port is a nice feature. Seems there would be people on both sides of the A+ VS B+ debate and the most obvious/best solution would be to design the next HM board so it would work with which ever rPi+ model you prefer. Leaving the standard rPi models behind is no big deal since you're not gonna see them around for long, and if you already have one the HMv4.2 is a GREAT board you can use with them...
 
Looking at Element14 here in Australia, they have 884 Raspberry Pi model B units currently in stock. These are going for AU$38, which at current exchange is about 10 US bucks! - well okay, maybe not, but approx US$32.
These are the Pi’s that Element14 make themselves, have used many with no problems.
I think Element14 is Newark in the US - maybe they can sell you a bunch?
 
Newark was the place I was trying to buy from at retail ($35). I also submitted a quote request for 100 but they also said they were discontinued. If the Pi foundation is still producing the B like they say, I'm not sure where they're sending them considering Newark/Element14 is their main distributor.
we’ll be keeping Model B in production for as long as there’s demand for it.
Click to expand...
I'll be the first to admit that the B+ is a B, just better. The only deficiency is that the B+ monopolizes edge space which probably isn't a problem for anyone but HeaterMeter which has a ton of I/O ports itself.
 
Hi guys,

As a newbie looking to buy/build my first HeaterMeter, would it make sense for me to wait to see what happens with the A+ / B+ before moving forward? I'm in Chicago so BBQing is basically on pause until the spring anyway.

Thanks for all of your hard work! I've been lurking for a while and finally signed up. The amount of time, effort, and dedication is both astounding and appreciated!

All the best,

Jeremy
 
If you can find a rPi B model at a decent price then I would say no need to delay, the HMv4.2 is an AWESOME board. If you can't find a B model at a decent price them perhaps wait, or you could always buy an A+ and build your HM with the few components on the other side of the board as Bryan detailed in this thread....
 
Functionally, it will be the same but the Plus version will almost certainly be larger or have connectors in strange places. The A/B version on a v4.2.4 board is the pinnacle of HeaterMeters I think.

Of course I could be wrong and the v4.3 will be the best version of HeaterMeter ever but I'm still trying to do basic layout so there's not telling what it will be like! You could keep your eyes open for a cheap Model B then if you decide to go B+ you can always ebay it and probably make your money back.
 
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