On 03/01/2020 11:42, Toby Newman wrote:
> On 2020-01-02, The Natural Philosopher  wrote:
>> On 02/01/2020 16:57, Toby Newman wrote:
>>> On 2019-12-20, nev young  wrote:
>>>> On 19/12/2019 13:02, Toby Newman wrote:
>>>>
>>>>
>>>>> This is a good present idea for my mum or sister.
>>>> Hi Toby.
>>>>
>>>>> How do you power it?
>>>> I power mine from an old (ie redundant) laptop power supply to deliver
>>>> ~ 19volts down a length of 10A two core cable. The sort used for hedge
>>>> trimmers or lawn mowers. I use such a high voltage and thick cable to
>>>> compensate for the voltage drop of the longish runs to the garden.
>>>>
>>>> At the camera end, this (highish) voltage is fed in to a buck dc-dc
>>>> converter eg. https://tinyurl.com/vbbbv8f  This delivers a good steady
>>>> supply of 5volts to the pi Zero W, camera and LEDs.
>>>> ( nb. DO NOT USE A 7805 voltage regulator. It'll get way too hot! )
>>>
>>>
>>> Cool, so do I have this right:
>>> Connect the 19V across the inputs, then a large
>>> resistor across the outputs, and use a multimeter to watch the voltage
>>> drop across the large resistor while twisting the potentiometer with a
>>> screwdriver until it matches 5V, then replace the resistor with the
>>> Raspberry Pi?
>>>
>> staggeringly bad way to do it
>>
>> read what he said.
>> "this (highish) voltage is fed in to a buck dc-dc converter eg.
>> https://tinyurl.com/vbbbv8f  This delivers a good steady
>> supply of 5volts to the pi Zero W, camera and LEDs."
>
> I think perhaps I omitted some words and you misunderstood my meaning.
> et me rephrase:
>
> Connect the 19V across the inputs of the buck dc-dc converter, then a large
> resistor across the outputs of the buck dc-dc converter, and use a multimeter
> to watch the voltage drop across the large resistor while twisting the
> potentiometer on the buck dc-dc converter with a screwdriver until it matches
> 5V, then replace the resistor with the Raspberry Pi?
>
>
Yes.Or alternatively buy a custom 5V only converter. Doesn’t need to be
buck from 19v

https://www.ebay.co.uk/itm/UK-UBEC-5V-6V-3A-RF-BEC-Switch-Mode-Lowest-Noise-Red
uction-Battery-Eliminator-RC/312566011043

These thongs produced in thousands to allow model avionics to work from
a motor pack that can be up to 50V



--
Labour - a bunch of rich people convincing poor people to vote for rich
people by telling poor people that "other" rich people are the reason
they are poor.

Peter Thompson

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