USB010 powering the Picaxe

gtslabs

Member
I read the datasheet on the USB010 and did not see any schematics. Can I get the 5 volts to power my picaxe chip by using this converter? What pin would it be on the DB9?
 

hippy

Senior Member
USB010 claims to support "the standard RS-232 Serial Interface" which means no dedicated power out line and signals which should be +12V/-12V. What comes out of the 9-way plug should be the same as what would come out of a 9-way socket on a PC chassis. You can check by voltages by using a multimeter.

You can often derive 5V from RS232 by diode mixing the RTS and DSR lines and running them through a low-dropout 5V regulator (LDO), however the amount of current you can draw is quite low, probably just enough for one or two Led's. The current available from the USB010 may be even less. Both require that the RTS and/or DSR lines are activated when the PICAXE is in use and that may not always be the case.

An alternative possibility is to put a power supply tap on the USB cable itself. A USB socket and plug with all four wires passed through with 0V/+5V from that should also work once the USB device has been detected and enabled. It is also possible to take 0V/5V from any other USB port ( limited to 100mA ).

Yet another alternative is a similar type of tap which can be used with a mouse or keyboard cable. These used to be quite common for some USB webcams but you can also build your own.

It is possible to take a 5V feed direct from the PC's PSU but that's definitely not recommended because the PSU can deliver huge amounts of current which can detonate PICAXE circuits under fault conditions or if you make a wiring error. If taking a feed from a PC PSU it is probably better to use a 5V regulator and draw current from the +12V line. You may need quite substantial heatsinking to cope with the regulator dropping 7V if drawing a reasonable amount of current.

As with the PC PSU connection, any fault on the PICAXE side could have a costly and permanently detrimental efect on your PC and data so care should always be taken when deriving power from a PC. USB and serial port derived power is usually safer because there is often current limiting in place to prevent or at least limit damage. Care has to be taken that any flying-lead PC power plug doesn't accidentally get shorted to something inappropriate.

The best solution perhaps depends upon what you need the power for; whether it's for developing and experimenting or a finalised PICAXE product.
 

Mycroft2152

Senior Member
It is possible to power other devices from the USB port. Here are a couple of commercial items:

Coffee Warmer
http://hopestar.en.alibaba.com/product/50088704/50290305/USB_warmer/USB_Coffee_Warmer.html

From the ThinkGeek Company:

Drink Chiller/warmer
http://www.thinkgeek.com/homeoffice/gear/957e/

Electric shaver
http://www.thinkgeek.com/gadgets/travelpower/93a6/

Missle Launcher
http://www.thinkgeek.com/geektoys/cubegoodies/86b8/

And of course the George Foreman USB powered Grilling machine:
http://www.thinkgeek.com/stuff/looflirpa/igrill.shtml

Myc Holmes
 

benryves

Senior Member
Without negotiation, a USB port can only supply up to 100mA, and only 500mA maximum current if the connected device requests it. Above this and the USB port will be disabled. This is why those USB phone charger adapters (and similar peripherals) don't actually work...
 

hippy

Senior Member
A USB port is able to provide up to 100mA (0.5W) and, if the controlled device has a genuine USB interface it should be able to instruct a powered hub ( sometimes the PC itself ) to deliver 500mA (2.5W).

Notionally, any USB connected device ought to honour the USB specification and go into low-power mode, but it seems that most USB systems do not enforce that.

The bottom line is that there's usually 100mA available per port.
 

inglewoodpete

Senior Member
Mycroft: I don't think any of us will live long enough to enjoy a 1/4 pound hamburger cooked on a George Foreman USB powered Grilling machine at 2.5W (max)!!

Back to the subject: it should be possible to run a PICAXE off the 5v from the USB but electrical 'noise' from the PC power supply will need to be smoothed to keep the PICAXE stable.
 

Mycroft2152

Senior Member
HI Pete,

:)

I couldn't resist.

It was a choice between the George Foreman Grill and a tanning bed. Both April Fool's Day product listings at ThinkGeek.

The others are legitmate products.

Myc
 

hippy

Senior Member
Well I was suckered. I managed - after scepticism and a bit of effort to overcome that I must add - to theorise that the George Foreman Grill could possibly work, even at 2.5W.

A continuous 2.5W may not cook your burger, but if it were stored up and then dumped in a short period it could have considerable heating effect. If that were physically stored ( the fire-brick effect of storage heaters ) the temperature could be held while the next charge built up again to give another blast of heat. Much like you cannot cook a burger with a candle or blatting it briefly once a minute with a blowtorch, you could however heat a fire brick once a minute and have it maintain its heat.

Entropy issues didn't seem to be a problem either - consider a Van de Graff generator, you slowly push charge into it but let it out quickly; sausages, burger and people cooked in a jiffy. The Forman Grill is also an enclosed unit, so heat transfers into the burger rather than escaping the system. It's only heat loss which stops a 100W light bulb heating a warehouse.

Tanning bed too; a small amount of power accumulated over a long period of time can be released as higher power over a shorter period of time.

The grill mentioned charging capacitors which is how I managed to arrive at a believed feasible way the product could work. So, have I really been suckered ?
 

BeanieBots

Moderator
I often meet statements such as "how hot could it possibly get with just 1W?".
Have a look at a 1W torch bulb filament. Hot enough to glow white!
 

hippy

Senior Member
@ Dippy et al : That's the big question isn't it : Am I losing it, or is a USB powered George Foreman Grill possible ? Just because they say it's an April Fool joke doesn't mean it is ( beyond such a device not actually being available for purchase ).

I don't mind being April-Fooled or proven wrong, neither would be a first. What does concern me ( first rant on the new Forum ) is that people will so often take things at face value with no questioning or analysis and no evidence to support or refute a particular claim. How often has 'the truth' been held up to ridicule and those who support it punished, killed and even tortured for doing so ? Let's not live in a world where truth is whatever someone tells us it is or defines it to be. Let's look at the facts. How often have we been told things are absolutely impossible only to later find they are possible ?

I thought of a different approach to showing it can be feasible ...

Can a GF Grill be mains powered; yes, we can buy them and use them.

Can a GF Grill be powered from batteries; yes, it can be mains powered so we can use batteries and a suitable mains invertor.

Can USB charge batteries; yes.

Could USB be used to charge batteries which could be used with an invertor to power a GF Grill; yes.

With a re-design of a mains-powered grill it could become even more feasible. That doesn't mean one could buy a USB GF grill, take it home, plug it in, power-up and start cooking, but so what ?

It's really a question of whether a USB GF grill is practical or not, not whether it could work. 2Wh input accumulated over 1000 hours can be converted to 2KWh for an hour less losses. I have no idea what a GF grill needs but let's guess at 1kW for 15 minutes, 0.25kWh. That would notionally require charging the batteries at 2.5Wh for 100 hours. That makes the Grill available for use once a week or so. Seems entirely feasible to me if not entirely useful for day-to-day living.

The question then is, are those who think a GF Grill could exist April Fools, or are those who say it is an April Fool the real April Fools ?

I'm open to being shot down in flames ( griddled to a crisp even ) by anyone who wants to show it is definitely impossible to create a USB powered GF Grill, but "not possible" carries little weight without supporting rationale. "Not practical" is entirely different to "not possible".
 

Dippy

Moderator
Someone call a Doctor quick! He REALLY Has lost it.
Calm down Dear. It'll be alright. George Foreman doesn't even know what a USB is.
Nurse, tighten those straps!
Tighter! He's breaking loose. (Even though some people here spell 'lose' as 'loose')
Oh Jeez, he's spotted a microprocessor ... he's escaping!

I think yer burger would have rotted before you cooked it using a USB/Charger.
I wonder how many Joules are required to cook one?
We'll also have to make some assumtpions concerning heat loss from the system too.

Just sit down, feet up and have a nice cuppa before Therodynamic Theory get's the better of you :) and please don't start the mathematical poof of the non-existence of God using Babel Fish mega-functions.

Right, I must go and charge up my car from an AA battery now.
What was that flying past my window. I'll be darned! It was a pig.

A fast neutron could get from New York to London in less than a second.
 

hippy

Senior Member
Someone call a Doctor quick! He REALLY Has lost it.
I'd appreciate being told where though and how ;-)

I'm not convinced it's actually an issue of thermodynamics, more one of accumulation and discharge of energy; you put the same in and you get nearly the same out, accumulation can be done over a longer time than discharge. Just like AA battery charging; charge at 20mA for a few hours to get 2000mA for an hour when used.

If I'm being an idiot and there's a flaw in that thinking then that's okay by me, but I don't see where that flaw is.
 

papaof2

Senior Member
"Solar powered nightlight" -
I have several (outside the house) that mark the edges of the walkway in front of the house and the corner of the retaining wall along the driveway in back of the house ;-)
Good for 4 to 8 hours, depending on the amount of sun received during the day.

You probably meant night lights *inside* the house ;-)
Try the fluorescent version:
http://www.amazon.com/Sunforce-81090-Solar-Shed-Light/dp/B000CIADL6
or the LED version with motion sensor:
http://www.amazon.com/Sunforce-82150-Solar-Motion-Light/dp/B000FIWKR8/ref=pd_bxgy_auto_text_b/105-6374277-6105250

Except for one light (at the bottom of the stairs to the basement), I'm gradually replacing all the 7W/4W bulb nightlights with 0.3W LED versions. Some versions are less reliable than others. I've had two failures of one model (single LED) in less than two years - one died (LED burned out - replaced with a high MCD white LED from LedShoppe.com and it's still working), the other started flickering a couple of times each second (haven't taken time to open it up yet). The nightlights with 3 white LEDs seem to be surviving longer. Using a solar panel to charge a battery to run white LEDs would be even better - I have all the parts, just have to find an incentive to run wiring...

John
 

Mycroft2152

Senior Member
HIppy,

I think you are over analyzing the problem and just digging yourself a deeper hole. )

Can we all agree to let Hippy have the last word, before this turns into another bunny thread.

Now if anyione wants to discuss a PICAXE based controller tostore and release power, I"m intersted.

Myc

PS. This process is the essence of the solar powered BEAM robots.
 
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BeanieBots

Moderator
@ papaof2. I meant exactly "Solar powered nightlight".
Not much point having a bulb lit by solar power:p
A unit that stores solar power and releases it at night is a touch more useful:rolleyes:
It's all about semantics.
 

andrew_qld

Senior Member
I remember seeing "solar powered night light" project using an incandescant torch bulb when I was a kid. Something like 12 hours of sunlight gave you 10 minutes of dim glow..
 

Dippy

Moderator
Just let hippy have the last word or else he'll write 200 lines about some French philosopher and/or Marx.
I'm pink therefore I'm spam etc.

Mr Marx I can't marry you, I'm married already. That would be bigamy.
Big-a-you? I think that would be big 'a me. ("Big of me" for non-Marxists).
 

hippy

Senior Member
HIppy, I think you are over analyzing the problem and just digging yourself a deeper hole.
Maybe, but all I need is someone to explain why and where that is ( with some factual scientific support ) rather than just saying it's not possible.
 

hippy

Senior Member
Just let hippy have the last word or else he'll write 200 lines about some French philosopher and/or Marx.
I'm pink therefore I'm spam etc.

Mr Marx I can't marry you, I'm married already. That would be bigamy.
Big-a-you? I think that would be big 'a me. ("Big of me" for non-Marxists).
It's not about having the last word it's about getting to the bottom of it. Can one take USB power and using technology cook a burger. A simple yes or no. I say yes and see nothing but ridicule in return, no refutation, no contrary explanation, no evidence to prove not. It's like a teacher writing "total crap, you tosser" on an essay; not very productive.
 

BeanieBots

Moderator
Could it be done? Yes, with a little help from power storage.
Could it be done with the unit advertised? No. Evidence = unit not large enough to hold enough energy for desired effect using today's technology.

Nesbit bought one. Didn't work:mad:
 

Dippy

Moderator
It's not ridicule hippy, it's just a bit of light-hearted ribbing.
Of course it COULD be done, hence my comment yesterday "You just need a big battery and plenty of time".

I had assumed you were just joshing...
A windscreen washer pump could fill a 10 miilion gallon tank and then you could open the sluices ino a water-mill and grind your flour.
It could be done , but a little impractical I would suggest.

It's always interesting to converse about the possibility of things. It's fun so don't stop, but let's not get too serious eh :)

Joules are usually the answer. From cooking to weapons.
 

manuka

Senior Member
This "Watts up" reminds me of the infamous electric fence cooker for farmers developed here by a final year Industrial Design student. His concept involved clipping leads to an electric fence, when way out on the farm,& cooking up a snack. He ran with the idea & spent ages building a gorgeous prototype BEFORE energy fundamentals were pointed out to him. The poor guy- he'd assumed 5kV jolts equated to energy in abundance. Of course each pulse is only a few Joules, & (with gaps of seconds between each) heating power thus averages ~1 Watt.

I annually quote this sad saga to those who neglect initial planning homework & concept evaluation. Many otherwise just crack open their toolbox & rush into soldering up a PCB...
 

beny1949

Senior Member
funny you shoulf all be talking about this.....

the other day in physics, we decided to cook a sausage with a power supply. our VERY experianced science teacher told us that the SHC of sausage meat is about 200Jg-1 per degree.

In my experiment i worked out it would take approximately 1 hour to cook a 7 gramm peice of sausage (tiny to you an me), just from passing a current of about 80mA i think it was...

Im with hippy, the usb grill is most certainly possible, but would be more of a slow cooker than grill, unless there was some way of storing the charge

Ben
 

Mycroft2152

Senior Member
Well start cooking it now - I'll be round to eat it in the Summer :)
Along with a side order of E. Coli and Salmonella!

Are only talking about a single USB port here? Why not use multiple ports?

I have a quad USB adapter that includes a 2 AMP wall wart power supply, getting warmer.

Maybe we could fry up some rabbit!

Nesbit Lives!
 
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