rjhazeld
Posts: 38
Joined: Mon Feb 16, 2015 9:19 am

3b+ battery?

Sun Apr 01, 2018 11:11 am

Decided to try my cambot with a 3b+ to get the benefit of better wi-fi range. Existing 9.6v battery running through a Thunderborg motor controller didn't work - output to pi is only 1.5 amp. Tried splitting the power to give a direct connection to the pi from a battborg regulator set up but that also doesn't work - I guess current limit is similar. Wondering whether a powerbank with a 3amp output might cut it.? Or is there a regulator that has higher current capacity?

rjhazeld
Posts: 38
Joined: Mon Feb 16, 2015 9:19 am

Re: 3b+ battery?

Sun Apr 01, 2018 10:59 pm

Spotted this regulator which apparently can go to 5amp: http://www.hobbytronics.co.uk/d24v50f5 ... gIgK_D_BwE . On the face of it this ought to work although a review suggests that it generates a fair bit of noise. Thoughts?

Idahowalker
Posts: 445
Joined: Wed Jan 03, 2018 5:43 pm

Re: 3b+ battery?

Mon Apr 02, 2018 1:38 am

rjhazeld wrote:
Sun Apr 01, 2018 10:59 pm
Spotted this regulator which apparently can go to 5amp: http://www.hobbytronics.co.uk/d24v50f5 ... gIgK_D_BwE . On the face of it this ought to work although a review suggests that it generates a fair bit of noise. Thoughts?
That the unit generates lost of noise might be an introduction of a number of interment issues that I would find unacceptable. Especially if the noise generated is under a nominal load, than the noise will just increase when the supply is placed under a greater load.

I did a search on Amazon and found a number of dc-dc converters for the Raspberry Pi that got good ratings. I did note that a few dc-dc converters listed for the Pi B did not work well with the B+, something to keep in mind as you shop around.

Are you trying to power the Pi from the USB ports? I noted the two ways to power the Pi from a dc to dc converter is from the regular power port (mini USB) or by directly feeding 5V to the 5V pin on the GPIO. The USB ports are limited in current and cannot supply the Pi with sufficient current to operate.
Without knowing why you are deleting my postings, I will not know how...

rjhazeld
Posts: 38
Joined: Mon Feb 16, 2015 9:19 am

Re: 3b+ battery?

Mon Apr 02, 2018 9:36 am

Thanks, I did see the review that talked about noise but wasn't sure whether that would be an issue for my purposes (the regulator could be sited with the battery below the metal deck of the vehicle. Clearly a 'quiet' unit would be better though.

The current setup feeds power via the 5v GPIO pin.

Idahowalker
Posts: 445
Joined: Wed Jan 03, 2018 5:43 pm

Re: 3b+ battery?

Mon Apr 02, 2018 11:47 am

rjhazeld wrote:
Mon Apr 02, 2018 9:36 am
The current setup feeds power via the 5v GPIO pin.
I am looking, at some point, to power the Pi from a battery source. Are you using your own wire and connector or a Dupont wire? I am thinking the Dupont wire would be kind of wimpy to carry, up to, 2 amps. If, for me and I understand the issues of using multiple power connection points, I'd use several Dupont wires from source to RPi-J8 pin 2 and 4. Better yet, I'd use a single beefier wire that would solder to RPi-J8 pin 2 and 4. I have my doubts about the Dupont wire connector having the surface area contact to a single GPIO pin to deliver 2amps.
Without knowing why you are deleting my postings, I will not know how...

rjhazeld
Posts: 38
Joined: Mon Feb 16, 2015 9:19 am

Re: 3b+ battery?

Tue Apr 03, 2018 5:34 pm

Noting the comments about noise I have gone for an adjustable dc:dc stepdown converter https://www.amazon.co.uk/dp/B015306ATQ? ... E_DDE_dt_1 which delivers up to 3amps. Chose this because it gives led output voltage/current display so I can see what is going on. Happy to say that so far it is working a treat, the pi boots up quickly and haven't had any issues yet.

Moe
Posts: 230
Joined: Sun Jan 25, 2015 2:44 pm

Re: 3b+ battery?

Tue Apr 03, 2018 7:52 pm

All cheapo PSUs and DC-DC converters are switchmode devices and wil generate a lot of noise. The problem signal is the switching frequency, which will be in the 10s or 100s of kHz, so propagation will be mostly conducted rather than radiated. This means your metal shield will not help, but a well-placed capacitor might. In any case, the Pi is pretty resilient and I've never had any problems.

You have a made a good choice I think - I always use at least 3A for a Pi 3 with add-ons, and an adjustable output allows you to compensate for inevitable volt drops.

Avoid Du Pont connectors; they are meant for experimenting, not building products. They should take 3A but I have found them to be very unreliable. The slightest vibration and the signal can drop out, which will cause crashes if you're using it for power. If you must use them, then multiple-way connectors are much better than single ones. The best way to power the Pi is the Mini USB port, because that's where the fuse is.
Submarine communication systems engineer and amateur robot enthusiast.

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