grats
Posts: 30
Joined: Fri Apr 25, 2014 6:51 am
Location: Colorado, USA

Re: Running multiple pi's on a tractor

Mon Jul 03, 2017 8:01 pm

Imperf3kt wrote:Monkey wrench:
Can your alternator handle the amperage?
Take for example my car - it has a 110A alternator in it (which is larger than a standard alternator as I own a v8). The battery has 90 minutes 'reserve'.

Essentially, if my alternator cannot supply enough current to everything in the car, my battery will be dead in 90 minutes.
The car and electronics use ~80A, leaving me ~30A buffer. What does your tractor use and how many A are left over? If it is less than 30-40A, you may find one day your tractor won't crank over.
30-40amps on 12 volts is NOT EQUAL TO 30-40amps in 5 volts.


Octradox wrote:
Imperf3kt wrote:You can do it like that, sure, but I imagine you'd need multiple buck converters. DC doesn't travel very far. 12M even, will be too far.
Can't I just have a big wire to minimise resistance?
yes, but the converters don't have big connection areas
Octradox wrote:
hortimech wrote:
Octradox wrote:

Ok, so it'll output 12 volt, do I just need to get it down to 5 volt with a buck down and it'll be fine?
Unfortunately it will not be 12v, it will be whatever the battery voltage is when engine is not running, rising to 13.8v when the engine starts with a fully charged battery, or 14.4 (or above) if the battery is fairly flat.
Ok, but do buck down converters have a bit of tolerance for this?
yes, I'd suggest an LED driving converter they have stable output if you're limiting by voltage. This will allow your battery to go all over the place (8volts - 18 volts) and your output should be relatively the same... 4.99 - 5.01

https://www.aliexpress.com/item/Lithium ... 62651.html

I run 25 of these and they haven't had any issues
these do have an amperage limit potentiometer so make sure you have that maxed out and limit them by the voltage instead (5 volts)
Octradox wrote:
Gavinmc42 wrote:I have a Pi security camera at the end of 20+m of cat 5 DIY PoE setup.
12Vin and a $2 12volt to 5V USB cigarette adapter, ripped open for the circuit.
Been working for years.

Only a 12m boom, thicker cable would be used and half the Pi's are only 6m away.
Pay a bit more and I would use TO-220 Voltage regulator Switch mode version of a LM7805.
Some have lowdrop out down to 5.5V and 36V? input, available from 500ma to 2amps+.

I will assume you are using Pi3 with camera for spot location spraying.
The 12Volt solenoids will need 1amp too?

You could use a Cat5 12V PoE but bunch of 12 cables per boom gets a bit big.
Hmm, actually cat5/6 cables can be got at various lengths for quite low prices, this could save a lot of cabling costs.

How are you controlling the Pi's Ethernet or RS485/CAN?

Yeah, 2 solenoids per meter. I'll have a look at some of the stuff you suggested.

I'm using the WiFi atm. Have one set as a server, using socket. Can even send altered video through. Helps with selecting the settings. Am a bit worried if the WiFi can handle all that/ the distance, but worst to worse, I'll hardwire it up Ethernet style.

Having lots of cables is fine. But if it's avoidable why would you do it.
https://www.amazon.com/Ubiquiti-NanoSta ... 004EGI3CI/
I have several of these covering 50 acres of land if you need more wifi.

if you run it on same channel, same wifi name, same everything as your other access points the clients (raspberry pi, phones, laptops whatever) will seamlessly switch to the strongest signal. (the same way college campus / high school works probably phone towers too)

OutsourcedGuru
Posts: 58
Joined: Mon Jun 19, 2017 11:15 pm

Re: Running multiple pi's on a tractor

Mon Jul 03, 2017 10:53 pm

If it were me, I'd start with a 15A car inverter and attaching that to the battery with an inline fuse (now AC in typical home-style 115VAC connection) and plug into that six of the Radio Shack USB chargers and power the first 24 Raspis using the typical USB style of connection. I'd treat the 25th monitoring point like it's not worth the trouble.

https://www.radioshack.com/products/rad ... ll-charger
And I'd try to find an inverter that already includes six power outlets.
(Plugging into the cigarette lighter will limit the current, btw.)

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