Powah!
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Powah!

by asgard on Tue Jan 29, 2013 11:24 pm

The subject field connects both the function of this teensy device, but I seem to have persistent earworms full of Tina Turner, for some odd reason :)

I got tired of constantly wearing out pins of my breadboard by pushing and pulling wires to do power switching, so I decided to make something better. This board is the Powah. It is approx. 1 cm^2 and is a simple on/off switch. I put the dc power, unswitched, to one rail of my breadboard, and feed it to the Powah. I then put the output from the Powah to the other DC rail in the breadboard. I looked all around for anything similar, but did not find anything except a module from Pololu, which was limited to 5V DC levels, was much larger than this, and did not have the .1-inch centered form-factor.
The current load when turned on is 3.06mA, while the load when turned off was not measurable by my admittedly primitive setup.

It is really not very sophisticated, as circuit designs go, but it certainly works for the purpose. I do not have any kind of video setup here, or I would attempt to show this at the next Show And Tell, but I hope this looks okay.
J.R. Stoner
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Attachments
2013-01-29_18-44-12_825.jpg
BDG P01-112 Powah, top view.
2013-01-29_18-44-12_825.jpg (26.44 KiB) Viewed 1906 times
2013-01-29_18-44-49_951.jpg
BDG P01-112 Powah, bottom view.
2013-01-29_18-44-49_951.jpg (38.39 KiB) Viewed 1906 times
P01-112C_Powah.jpg
BDG P01-112 Powah, schematic.
P01-112C_Powah.jpg (35.36 KiB) Viewed 1906 times
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Re: Powah!

by adafruit_support_bill on Wed Jan 30, 2013 7:41 am

I seem to have persistent earworms full of Tina Turner

I was expecting to see Darth Sideous
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Unlimited Powah!
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Re: Powah!

by lenacole on Thu Mar 14, 2013 5:49 am

that's a complicated graphics. Woo!
Last edited by lenacole on Mon Mar 18, 2013 8:36 am, edited 2 times in total.
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Re: Powah!

by tastewar on Thu Mar 14, 2013 12:58 pm

Sorry, I'm not understanding something from the description, because it would seem to me that you could accomplish the same thing with a switch alone. Is it hard to find breadboard friendly push-on/push-off switches? Or is it the integrated LED? Or am I missing something else? Couldn't this (https://www.adafruit.com/products/805) effectively do the same thing? Or is it the current rating? Just curious...
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Re: Powah!

by adafruit_support_mike on Thu Mar 14, 2013 6:02 pm

tastewar wrote:Sorry, I'm not understanding something from the description, because it would seem to me that you could accomplish the same thing with a switch alone. Is it hard to find breadboard friendly push-on/push-off switches?

Not hard, but definitely expensive.

A push-on/push-off switch is a fairly complicated little machine, and you pay for it accordingly: http://www.mouser.com/ProductDetail/ALP ... bqXVdeE%3d ($1.25 each when you buy lots of 1000)

6mm tact switches are $8 per hundred: http://www.mouser.com/ProductDetail/TE- ... wmrWw7o%3d

The design above (which is pretty nifty) converts a tact switch into a 'soft switch' capable of the press-on/press-off action people have come to expect. I use something similar, but never considered cranking it into a form factor that small.

Bravo!
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Re: Powah!

by asgard on Thu Mar 14, 2013 8:55 pm

Not to mention it is small enough to mount in small places (without the pins) for use as a limit sensor. Such as the inside rails of a MakerBot or somesuch.
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Re: Powah!

by tastewar on Thu Mar 14, 2013 10:17 pm

mstone@yawp.com wrote:
tastewar wrote:Sorry, I'm not understanding something from the description, because it would seem to me that you could accomplish the same thing with a switch alone. Is it hard to find breadboard friendly push-on/push-off switches?

Not hard, but definitely expensive.

A push-on/push-off switch is a fairly complicated little machine, and you pay for it accordingly: http://www.mouser.com/ProductDetail/ALP ... bqXVdeE%3d ($1.25 each when you buy lots of 1000)

6mm tact switches are $8 per hundred: http://www.mouser.com/ProductDetail/TE- ... wmrWw7o%3d


Certainly, the tact switch alone is cheap, but adding in the other components, the board, the assembly time or cost, do you really come out ahead on cost?

mstone@yawp.com wrote:The design above (which is pretty nifty) converts a tact switch into a 'soft switch' capable of the press-on/press-off action people have come to expect. I use something similar, but never considered cranking it into a form factor that small.

Bravo!


Agreed! Very cute & clever (I'm sure; certainly beyond what I could do). I'm still left wondering -- does it do more than a push-on/push-off? Is it debounced, or does it handle more current, or ???

I'm not trying to be negative, I'm genuinely curious about the value or intent. If it's intellectual curiosity, or just plain coolness, I can understand those, too.
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Re: Powah!

by Zener on Fri Mar 15, 2013 12:04 am

I think the .1uF cap is the denounce, and it also has the LED indicator. I think they are neat enough. If they were a few bucks I think people would buy them.
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Re: Powah!

by adafruit_support_mike on Fri Mar 15, 2013 1:50 am

tastewar wrote:Certainly, the tact switch alone is cheap, but adding in the other components, the board, the assembly time or cost, do you really come out ahead on cost?

Yep. For the ones I make, the total parts cost is about 20c.

tastewar wrote:Agreed! Very cute & clever (I'm sure; certainly beyond what I could do). I'm still left wondering -- does it do more than a push-on/push-off? Is it debounced, or does it handle more current, or ???

Yes, this circuit does debounce the switch. The power from this circuit will have the nice, glitch-free on/off transitions that are important for getting logic circuits to start in a known state. To get equally good transitions from a slide switch or latching pushbutton, you'd have to follow it with a debounce circuit that contains almost as many components, with their associated board space and assembly costs.

As power goes, you could use this to drive a few 40A power mosfets if you wanted to, but that's kind of a red herring.. you could drive the mosfets with a mechanical latch as well.

The big advantage of the general circuit is that it turns the circuit's power state into a signal you can control electronically. You could use this to power a 555 timer with a 5-minute delay, then have the 555 send U1A's output HIGH, killing the power. The result is an auto-off function that would be hard to implement with a slider or latching pushbutton. You can connect a diode to the top of C1 and get an enable/disable feature that keeps the circuit from turning on or off until some external condition is met.. again, hard to do with a mechanical latch. You can wire multiple switches in parallel and control the circuit from several different places.

And yes, in this instance, there's fair bit of "whoa, cool!" factor. ;-)
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Re: Powah!

by tastewar on Fri Mar 15, 2013 8:03 am

Thanks for the explanation!
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Re: Powah!

by asgard on Fri Mar 15, 2013 11:19 am

The next, obvious, question is this: what would be your level of pain for buying a Powah, and how many would you likely be buying?

Understand that to take this from prototype to production requires me to panelize at least 150 of them per panel, then send that to a pick and place shop for production. I don't think LadyAda's shop has the capacity to buy somebody else's design and put it on the website, although that is an attractive option, if available. I have finished design and am ready to test a newer Powah which has the capability of switching up to 18V, and has different turn-on and turn-off button press requirements, at the cost of a teensy bit bigger board. Things to ponder, since my interests have expanded beyond these devices significantly (see the other discussion I have having about threaded inserts and wireless power).
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Re: Powah!

by WethaGuy on Fri Mar 15, 2013 12:13 pm

asgard wrote:...buy somebody else's design and put it on the website, although that is an attractive option, if available...


hmm.... maybe you should consider not using the OSH gear logo if you intend to license the design. The copyright on the front of the board also appears to be at odds with the concept of OSH. The gear logo is usually used as a symbol denoting the design is open and available to all to reproduce or mod.
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Re: Powah!

by modeller on Fri Mar 15, 2013 12:38 pm

asgard wrote:The next, obvious, question is this: what would be your level of pain for buying a Powah, and how many would you likely be buying?


I think it's a neat item. What would I pay for it? Not much really, just speaking for myself, it would be more a luxury or little novelty because as you said I can just pull a wire and turn off the breadboard.

Oh I guess if I saw it on Ebay (not having seen it here) I'd say "Cool little item - but how much is it?). So I'd want it initially sans seeing the price. I'd probably give $5 or so for it, just for the heck of it because it's neat. I doubt I'd give $10 though. Just going by impulse shopping reactions.
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Re: Powah!

by Zener on Fri Mar 15, 2013 12:46 pm

asgard wrote:The next, obvious, question is this: what would be your level of pain for buying a Powah, and how many would you likely be buying?

An old rule of thumb for retail pricing is 5x the parts. I don't know that I personally would ever buy any but I think people can use such a thing. I am thinking you could have singles as you have shown, duals, 4x and 8x. Pricing something like 5.00, 7.50, 10.00, 12.50 respectively. So that is in line with what modeller just said (while I was still writing this reply.) If it's open source then I don't think anyone has to pay for the design. I don't know all the details there, but I would be happy with the bragging rights personally. Of course, with the round corners, Apple will likely claim they own the whole thing...
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Re: Powah!

by BruceF on Fri Mar 15, 2013 1:00 pm

WethaGuy wrote:
asgard wrote:...buy somebody else's design and put it on the website, although that is an attractive option, if available...


hmm.... maybe you should consider not using the OSH gear logo if you intend to license the design. The copyright on the front of the board also appears to be at odds with the concept of OSH. The gear logo is usually used as a symbol denoting the design is open and available to all to reproduce or mod.


Zener wrote:If it's open source then I don't think anyone has to pay for the design.

Yeah maybe, but see point number one in Phil Torrone's article on the subject of OSH licensing in Make.
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