This page (revision-18) was last changed on 2019-12-23 11:17 by Murray Altheim

This page was created on 2019-12-23 04:14 by Murray Altheim

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
18 2019-12-23 11:17 9 KB Murray Altheim to previous
17 2019-12-23 11:16 9 KB Murray Altheim to previous | to last
16 2019-12-23 11:12 9 KB Murray Altheim to previous | to last
15 2019-12-23 11:10 9 KB Murray Altheim to previous | to last
14 2019-12-23 11:04 9 KB Murray Altheim to previous | to last
13 2019-12-23 11:02 9 KB Murray Altheim to previous | to last
12 2019-12-23 11:01 9 KB Murray Altheim to previous | to last
11 2019-12-23 10:57 9 KB Murray Altheim to previous | to last
10 2019-12-23 05:18 9 KB Murray Altheim to previous | to last
9 2019-12-23 05:17 9 KB Murray Altheim to previous | to last
8 2019-12-23 05:16 9 KB Murray Altheim to previous | to last
7 2019-12-23 05:09 9 KB Murray Altheim to previous | to last
6 2019-12-23 04:58 9 KB Murray Altheim to previous | to last
5 2019-12-23 04:57 9 KB Murray Altheim to previous | to last
4 2019-12-23 04:53 9 KB Murray Altheim to previous | to last
3 2019-12-23 04:28 7 KB Murray Altheim to previous | to last
2 2019-12-23 04:20 7 KB Murray Altheim to previous | to last
1 2019-12-23 04:14 6 KB Murray Altheim to last

Page References

Incoming links Outgoing links
Power Supplies...nobody
PowerSupplies

Version management

Difference between version and

At line 14 changed one line
[{Image src='USBPowerSupplies/nuclear.jpg' caption='Serious Power' alt='serious power' align='right' class='imgFloatRight'}] There are a number of companies providing USB Power Supplies specifically for the Raspberry Pi. Each of the Raspberry Pi models has different power requirements (see below), with recommended PSU (Power Supply Unit) current capacities ranging from 700mA for the Model A to 3 amps for the Pi 4, but these numbers don't include sensors or motors.
[{Image src='PowerSupplies/nuclear.jpg' caption='Serious Power' alt='serious power' align='right' class='imgFloatRight'}] There are a number of companies providing USB Power Supplies specifically for the Raspberry Pi. Each of the Raspberry Pi models has different power requirements (see below), with recommended PSU (Power Supply Unit) current capacities ranging from 700mA for the Model A to 3 amps for the Pi 4, but these numbers don't include sensors or motors.
At line 18 changed one line
[Jaycar|Vendors] sell a ''[Mean Well 70W 5V 14A Power Supply|https://www.jaycar.co.nz/mean-well-70w-5v-14a-power-supply/p/MP3289]'' that actually delivers 70 watts (5 volts at 14 amps, do the math) for NZ$54.90. It's not as pretty as the Apple unit but as a bench power supply it looks pretty good. Here's the specs:
! Some Pi Power Requirements
At line 20 added 16 lines
Shown below is a portion of the table from the [Raspberry Pi FAQ|https://www.raspberrypi.org/documentation/faqs/#pi-power]. There's also a table showing typical power usage "during standard processes" (which doesn't include driving your robot up a steep incline). They define a "stressed" Raspberry Pi 3B as using 1.34 amps. Stall current on a robot motor can be 5 amps. Most robots have at least two motors.
Hmm. Clearly we need to think about this a bit more.
%%small
|| Product || Recommended PSU Current || Maximum USB peripheral draw || Typical bare-board consumption
| Raspberry Pi Model A+ | 700mA | 500mA | 180mA
| Raspberry Pi Zero W | 1.2mA | Limited by components | 150mA
| Raspberry Pi 3 Model B+ | 2.5A | 1.2A | 500mA
| Raspberry Pi 4 Model B | 3.0mA | 1.2mA | 600mA
%%
! A Potential Bench Power Supply
[Jaycar|Vendors] sell a ''[Mean Well 70W 5V 14A Power Supply|https://www.jaycar.co.nz/mean-well-70w-5v-14a-power-supply/p/MP3289]'' that actually delivers 70 watts (5 volts at 14 amps, do the math) for NZ$54.90. It's not as pretty as the Apple unit but as a bench power supply it looks pretty good. Here's the specs: [{Image src='PowerSupplies/bench-supply.png' caption='The Mean Well Power Supply: not so pretty' alt='mean well bench supply' align='right' class='imgFloatRight' style='margin-right:15%'}]
At line 36 removed one line
!
At line 38 removed 12 lines
%%small
|| Product || Recommended PSU Current || Maximum USB peripheral draw || Typical bare-board consumption
| Raspberry Pi Model A+ | 700mA | 500mA | 180mA
| Raspberry Pi Zero W | 1.2mA | Limited by components | 150mA
| Raspberry Pi 3 Model B+ | 2.5A | 1.2A | 500mA
| Raspberry Pi 4 Model B | 3.0mA | 1.2mA | 600mA
%%
The above is a portion of the table from the [Raspberry Pi FAQ|https://www.raspberrypi.org/documentation/faqs/#pi-power]. There's also a table showing typical power usage "during standard processes" (which doesn't include driving your robot up a steep incline, but might be helpful...). They define a "stressed" Raspberry Pi 3B as using 1.34 amps. Stall current on a robot motor can be 5 amps.
Hmm. Clearly we need to think about this a bit more.
At line 53 changed one line
My dad used to really like trying to guess what was in his Christmas gifts. I remember one Christmas where as a joke I gave him an extremely heavy transformer from a [Bell UH-1 Iroquois helicopter|https://en.wikipedia.org/wiki/Bell_UH-1_Iroquois] that I'd bought at a local surplus store (I wanted the chassis it was in, or some such reason). I'd put his real gift under the transformer and there were some laughs, ha ha. He then picked up the transformer and dropped it into what he thought was an empty box full of wrapping paper, except it wasn't empty. It contained the Rotal Albert tea cup I'd just given my mom. Ugh.
My dad used to really like trying to guess what was in his Christmas gifts. I remember one Christmas where as a joke I gave him an extremely heavy transformer from a [Bell UH-1 Iroquois helicopter|https://en.wikipedia.org/wiki/Bell_UH-1_Iroquois] that I'd bought at a local surplus store (I wanted the chassis it was in, or some such reason).
I'd put his real gift under the transformer and when he opened it there were some laughs, ha ha. For a minute. He then picked up the transformer and dropped it into what he thought was an empty box full of wrapping paper, except it ''wasn't empty''. It contained the Royal Albert tea cup I'd just given my mom. Ugh. — [Murray]
At line 56 changed one line
Some power supplies (what we might call "old school") use a [transformer|https://en.wikipedia.org/wiki/Transformer] to convert the wall voltage (110 volts in the Canada, the US and Japan, 200-240 volts in most of the rest of the world) down to the low voltage (5-12 volts) used for our robot. The more power we needed, the larger the transformer. The amount of power that could be delivered was almost a direct relation to the size the transformer. Transformers can get big and heavy.
Some power supplies (what we might call "old school") use a [transformer|https://en.wikipedia.org/wiki/Transformer] to convert the wall voltage (110 volts in the Canada, the US and Japan, 200-240 volts in most of the rest of the world) down to the low voltage (5-12 volts) used for our robot. The more power we needed, the larger the transformer. The amount of power that could be delivered was almost in direct relation to the size the transformer. Transformers can get big and heavy.
At line 58 changed one line
A __[Switching Power Supply|https://en.wikipedia.org/wiki/Switched-mode_power_supply]__ (also called a "switched-mode power supply) doesn't use a big transformer. Most laptop power supplies are switching power supplies. If you're on one of the robot vendor web sites you'll see switching power supplies advertised. AdaFruit sells a 5 volt 10 amp for US$30, another one for $25. Most of these units have the benefit of being able to run from either 110 or 240 volts.
A __[Switching Power Supply|https://en.wikipedia.org/wiki/Switched-mode_power_supply]__ (also called a "switched-mode power supply) doesn't use a big transformer. Most laptop power supplies are switching power supplies. If you're on one of the robot vendor web sites you'll see switching power supplies advertised. AdaFruit sells a 5 volt 10 amp for US$30, another one for $25. Most of these units have the benefit of being able to run from either 110 or 240 volts.
At line 65 added 2 lines
The only issue is that most of them don't end in a USB connector but rather a male DC plug; you'd have to convert that to a micro USB male, which is what's on most microcontrollers. Perhaps we need a [Recipe] on
[how to convert power from DC male plug to micro USB|HowToConvertPowerFromDCMalePlugToMicroUSB]...
At line 68 added one line
At line 64 changed one line
products. Apple seems to be the worst: they sell two adapters (listed as the ''Apple 87W USB-C Power Adapter'' and the ''96W USB-C Power Adapter'') that are likely the most expensive on the market and are not showing their output ratings in watts but seemingly their power ''requirements'', i.e, not what they __deliver__ but what they __use__. Of course it says nothing about this on the box. It's 87 watts, right? [{Image src='USBPowerSupplies/5w-adapter-thumb.png' link='https://support.apple.com/library/content/dam/edam/applecare/images/en_US/accessories/Adapters/5w-adapter-tech-spec.png' caption='Apple 5 watt USB adapter' alt='Apple 5 watt USB adapter' align='right' class='imgFloatRight'}]
products. Apple seems to be the worst: they sell two adapters (listed as the ''Apple 87W USB-C Power Adapter'' and the ''96W USB-C Power Adapter'') that are likely the most expensive on the market and are not showing their output ratings in watts but seemingly their power ''requirements'', i.e, not what they __deliver__ but what they __use__. Of course it says nothing about this on the box. It's 87 watts, right?
At line 70 changed one line
[{Image src='USBPowerSupplies/12w-adapter-thumb.png' link='https://support.apple.com/library/content/dam/edam/applecare/images/en_US/accessories/Adapters/12w-adapter-tech-spec.png' caption='Apple 12 watt USB adapter' alt='Apple 12 watt USB adapter' align='left' class='imgFloatLeft'}] To give you an idea of how far this is off from that advertised 87 watt promise, delivering 87 watts at 5 volts it should be delivering __17.4 amps__. Apple's unit is clearly using 87 watts to deliver 15 watts (3 amps at 5 volts) of power. You can check this yourself by using an online [Watts to Amps Calculator|https://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.html] or [Amps to Watts Calculator|https://www.rapidtables.com/calc/electric/Amp_to_Watt_Calculator.html].
To give you an idea of how far this is off from that advertised 87 watt promise, delivering 87 watts at 5 volts it should be delivering __17.4 amps__. Apple's unit is clearly using 87 watts to deliver 15 watts (3 amps at 5 volts) of power. You can check this yourself by using an online [Watts to Amps Calculator|https://www.rapidtables.com/calc/electric/Watt_to_Amp_Calculator.html] or [Amps to Watts Calculator|https://www.rapidtables.com/calc/electric/Amp_to_Watt_Calculator.html].
At line 72 removed 2 lines
What's strange is that Apple has delivered honest reporting on its other units. Their tiny 5 watt unit delivers 5 volts at 1 amp. Their 12 watt unit delivers 5.2 volts at 2.4 amps. They provide technical specification for these smaller models, but the "Tech Specs" for the 96 watt model just says "USB C". What gives?
At line 85 added 3 lines
[{Image src='PowerSupplies/5w-adapter-thumb.png' link='https://support.apple.com/library/content/dam/edam/applecare/images/en_US/accessories/Adapters/5w-adapter-tech-spec.png' caption='Apple 5 watt USB adapter' alt='Apple 5 watt USB adapter' align='left' class='imgFloatLeft' style='margin-right:2em'}] What's strange is that Apple has delivered honest reporting on its other units. Their tiny 5 watt unit delivers 5 volts at 1 amp. Their 12 watt unit delivers 5.2 volts at 2.4 amps. They provide technical specification for these smaller models, but the "Tech Specs" for the 96 watt model just says "USB C". What gives?
At line 96 added one line
[{Image src='PowerSupplies/12w-adapter-thumb.png' link='https://support.apple.com/library/content/dam/edam/applecare/images/en_US/accessories/Adapters/12w-adapter-tech-spec.png' caption='Apple 12 watt USB adapter' alt='Apple 12 watt USB adapter' align='right' class='imgFloatRight'}]
This page (revision-18) was last changed on 2019-12-23 11:17 by Murray AltheimTop