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?


--
-Toby
Add the word afiduluminag to the subject to circumvent my email filters.

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