PowerTwig......... A 5v/3.3v 800mA power supply on a 1/4"x3" PCB

WBA Consulting

Here's a peek at a new PCB, nicknamed the PowerTwig, that was designed with/by a good friend of mine. The concept has been in the back of my mind for over a year and since he had a PCB with a simple dual power circuit already in use, he harvested that for my concept.

The 5 volt and 3.3 volt outputs are based upon the reference design of the LD1117 using the improved ripple rejection circuit. The 3.3 volt circuit input is coming from the 5 volt output, so the 800mA rating is a combined total current output. By using an adjustable LD1117, you can modify resistor values for other output voltages.

The first few PCBs are awaiting parts install so that the design check can be completed. Once everything is set a release timeline will be available. Right now, it appears that the first batch of PCBs will be in my hands in late Feb.

Attached is a 3D view from Altium Designer (CAD software used for the design) and a picture with a PCB next to a gerber printout and a propstick.

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

Post Edited (WBA Consulting) : 7/22/2010 2:40:47 PM GMT

davejames

Nice - quite compact.

What range of input voltage will the Twig tolerate?

The LD1117 by J1 is the 5V regulator and the one by J2 is the 3.3V?

What's the free-air power dissipation of the LD1117?· At 8V input, the 5V regulator will see a 3V drop and at 800mA, that's 2.4W.· Will there be enough heat sink to accomodate this?


DJ

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Post Edited (davejames) : 1/12/2010 11:49:55 PM GMT

WBA Consulting

The LD1117 has a max input voltage of 15 volts, but as you mention, the higher the drop, the greater the power dissipation. It is rated for a max of 12w for power dissipation, but in free air the device is stable while operating at 125C for up to 1000 hours. This design is not really meant for pushing the limits of the LD1117, but in the original circuit that only had an oversized pad for the tab, it ran from 12v pushing 310mA for 12 hours a day for 5 weeks.

The main part of my testing will be with varying loads and input voltage levels to see how much it heats up. The maximum output current for the LD1117 is rated at 1.3A and one of my test PCBs will be subjected to that limit.

J1/J2 is the input. (2 pin header or DC jack)
J3 is the 5v output header
J4 is the 3.3v output header

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
Propeller-Based Reverse Geo-Cache Birthday Present Project

davejames

WOW - a very impressive device.

Thanks for the follow up info.

DJ

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WBA Consulting

First one built. Looks just like the 3d concept image, so that makes me like Altium even more. Haven't done any testing other than power up, but hopefully I will be able to put this one under varying loads over the next few days.

Input: 12.04v (12v power supply, not a wall wart)
Out1: 4.95v (121 and 360 ohm for divider values of LD1117 circuit)
Out2: 3.27v (121 and 196 ohm for divider values of LD1117 circuit)

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
Propeller-Based Reverse Geo-Cache Birthday Present Project

mctrivia

i am not a fan of linear regulators but that is a beautiful board design.

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24 bit LCD Breakout Board now in. $24.99 has backlight driver and touch sensitive decoder.

WBA Consulting

mctrivia, thanks. Funny thing is that the dimensions of the board are based upon a limitation of getting the PCBs made at extremely low cost by combining it with another project. All in all it worked out nicely. While holding the built board and another in my hand last night, I discovered that I could mount a second board back to back with the first and create a four output stick. Might be a thought for Prop2 which has a 1.8v requirement. (although I have another switching power supply setup that is capable of 1.5 amps on each of its 3 outputs (5/3.3/1.8). That design may make it to a PCB after Prop2 is released)

I already came up with a design improvement. Had I used 1206 size parts for the resistors in the divider networks, they would be much easier for end users to modify for other output voltages. I would like to sell this in kit form mainly, but I am uncertain as to how many people are comfortable with 0603 parts.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
Propeller-Based Reverse Geo-Cache Birthday Present Project

Post Edited (WBA Consulting) : 1/15/2010 5:36:17 PM GMT

mctrivia

0603 are easy to solder if given the right instructions.
I also have a 5/3.3/1.8@1.5 amp each supply designed. It is going to pcb soon on a board I designed for a customer.

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24 bit LCD Breakout Board now in. $24.99 has backlight driver and touch sensitive decoder.

James Long

WBA Consulting said...
mctrivia, thanks. Funny thing is that the dimensions of the board are based upon a limitation of getting the PCBs made at extremely low cost by combining it with another project. All in all it worked out nicely. While holding the built board and another in my hand last night, I discovered that I could mount a second board back to back with the first and create a four output stick. Might be a thought for Prop2 which has a 1.8v requirement. (although I have another switching power supply setup that is capable of 1.5 amps on each of its 3 outputs (5/3.3/1.8). That design may make it to a PCB after Prop2 is released)

I already came up with a design improvement. Had I used 1206 size parts for the resistors in the divider networks, they would be much easier for end users to modify for other output voltages. I would like to sell this in kit form mainly, but I am uncertain as to how many people are comfortable with 0603 parts.

Although I know it is an after thought, you may want to consider making the board fit a breadboard. That would be nice to have a 3.3 volt rail and a 5.0 volt rail. It would probably require a redesign.

James L

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James L
Partner/Designer
Lil Brother SMT Assembly Services

Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!

WBA Consulting

@mctrivia: agreed, my concern is with how many people are comfortable due to the size (IE: if they don't have a scope, etc).

@james: I never thought of the breadboard fit for this design until I received the first fabs and realized that it almost does fit on my small breadboard. With the limitations of the 1/4"x3" it may be possible to make that change. For now, the first 300 PCBs are made so any changes would be after those clear out.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
Propeller-Based Reverse Geo-Cache Birthday Present Project

WBA Consulting

Here's a picture of the dual output switcher circuit that I am looking at possibly doing in a few months (with the help of the same friend from the PowerTwig) It's based on the LT1940L and takes up a bit more real estate, but is much more efficient.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010
Propeller-Based Reverse Geo-Cache Birthday Present Project

Vaati

Wow--cool power supply!
The one thing I would be worried about is breaking it...

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Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!

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WBA Consulting

If anyone cares, sort of an update:

I have 60 boards ready to build and will have all material next week. My stencil will be ordered Monday and if things go well, the boards will be built the following week.

For now, it will be offered with all SMT parts installed for a 5v/3.3v arrangement. The DC jack and 2 pin headers will not be loaded, but included with the PowerTwig.

Each board will be tested using a 300mA load on each output.

Shipping in the U.S. will be $1.00 in a padded envelope.

I still haven't settled on a price, but will within a week. This isn't a money maker, so it will be kept low. Similar power supplies designed for breadboards run from $9.95 (PRT-00114 Sparkfun) to $13.99 ( MKCI1 MakerShed). I have to review things again, but I think I can beat $9.99. Plus, mine isn't so much designed for use on a breadboard as it is meant to enable an easy way to put a finished project in a box using a 12 or 9 volt battery and only need a basic prop circuit on a piece of prototyping board.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
Special Olympics Polar Bear Plunge, Mar 20, 2010

WBA Consulting

Here's a picture of the first two production units. These are in a fixed 5v/3.3v setup. Instead of using the LD1117-ADJ, I am using fixed 5v and 3.3v parts and eliminates the odd value resistors for the voltage divider setups. (easier to source parts).

These will be on sale at UPEW for a special price of $10. This will include:
1 powertwig built up as shown in the picture
1 DC Jack, 2.1mm
3 Two pin headers

A few of these will be in the raffle as well.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

WBA Consulting

Production is in full swing! First 90 units are in the first picture. The 6 gold-flash units in the lower right will be part of the raffle for UPEW.

The second picture is of the kit contents (DC Jack, three 2 pin headers, and the PowerTwig)

The last picture is the modification needed for the DC jack. It will be supplied with all three pins left on in case you want to use it for something else and use the 2 pin header for input to the PowerTwig. For use on the PowerTwig, just bend the side leg up until it breaks from the housing since it is not used.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

WBA Consulting

.....and the domain is active, so I guess I need to get details up soon. For now, I have the picture up.

www.powertwig.com

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

Post Edited (WBA Consulting) : 6/21/2010 12:48:02 AM GMT

HollyMinkowski

I hope you do well with this project.

I like the way this power supply looks, it's cute!

NWCCTV

So, What exactly does this do?

Unknown

Is there a different form factor that you could make?

Could you produce a version for people with batteries?· I'm thinking of 9 volt·or 6 volts (1.5 AA batteries times 4).

I'll probably just use a voltage regulator until then.

Post Edited (Chuckz) : 6/27/2010 4:19:09 AM GMT

WBA Consulting

NWCCTV: This is a power supply module that take a 6-15v input and provides regulated outputs at 5v and 3.3v.

Chuckz. I am not sure I understand your question, because this can be used with batteries. I am using one with a 9 volt battery for my plungelogger and in the same way for the metronome (see the links in my signature). The DC jack is supplied unsoldered so you have the option of using it with or without a wall wart. With a 9 vot battery, just solder the wires from the battery clip to the 2 pin header right behind the DC jack (J2 location). The square pads are all tied to ground.

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

WBA Consulting

UPDATE: I now have about 150 ready for sale. A box with some will be on it's way very soon to Gadget Gangster as well. The normal price for the PowerTwig will be $11.99, but for the first few weeks, they will be offered at the UPEW2010 price of $10. The exact expiration of the "sale price" will be posted on the Gadget Gangster product page. I'll have a PayPal button on the PowerTwig.com site in the next few days, but I can send a PayPal invoice to anyone currently interested. Shipping is a flat $2 for any qty.

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

eod_punk

Think I might have to get one of these. How long and wide is the powertwig? Distance between the headers too?

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There is no problem that can't be solved with a suitable amount of explosives!

EOD Memorial

WBA Consulting

Here's a the current dimensioned graphic for the board DWG. Locations were never reviewed for fit to breadboards, etc, so spacing is oddball. Luckily, the two outputs are very close to an inch apart, so it could straddle two busses of a breadboard as long as they are split in the middle (like most breadboards). If I make a V2, the overall dimensions will remain the same, but the spacing between headers would be locked into 0.100" grids. This version was really designed for off-breadboard use with wires soldered to the outputs.

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

WBA Consulting

U.S. buyers can now purchase from the PowerTwig website. PM me if you are outside the US for a customized PayPal invoice.

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Andrew Williams
WBA Consulting
PowerTwig Dual Output Power Supply Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

WBA Consulting

Now available at Gadget Gangster for $9.95!

http://www.gadgetgangster.com/find-a-project/56?projectnum=358

schill

WBA Consulting wrote: »

Locations were never reviewed for fit to breadboards, etc, so spacing is oddball. ... If I make a V2, the overall dimensions will remain the same, but the spacing between headers would be locked into 0.100' grids.

It never occurred to me to check the spacing between those headers. I guess I assumed they'd both be usable with a breadboard. I was thinking about placing them across the breadboard and using jumpers to get to the bus on either side (3.3 on one side, 5 on the other).

It's a nice looking board and I'm sure I'll be able to adapt the ones I ordered, but I look forward to a V2 with the "fixed" spacing.

WBA Consulting

Schill: Sorry for the inconvenience with the spacing. The breadboard spacing was never a thought of mine since the original design was meant for project cases, etc. Anyhow, the two output headers will fit into a breadboard with split rails with a slight bend inward because they are spaced 1.05" apart from each other.

I am working on a "connection kit" that will be added to future PowerTwigs. It will consist of a set of six 6" long wires with Molex SL crimps on one end and tinned wires on the other. 3 will be red and 3 will be black. Three 2 pin housings will also be included. This will enable you to have wires coming from the PowerTwig to plug into breadboards, etc. It will greatly increase the use of the PowerTwig. I am also looking at using Tyco MTA connectors in place of the Molex SL, because that involves a single part that requires less time to attach wires. I'll update this thread when I get there and will make sure you get a set(s).

Microcontrolled

I've recently gotten one of these and it is GREAT. I think it's a must have for any workbench. Expecially ones with lots of breadboard setups.

WBA Consulting

I finally decided on a connector to use for the leads for the PowerTwig modules; a 2 pin Amp MTA connector. I built one up at lunchtime today and I think it will work well.
My plan is to have two of the cables with each PowerTwig so they can be used for the outputs. The cables are made from 24AWG zip wire with the white stripe meant to be used as positive and connected to pin 1 of the connector.
The "PowerTwig with Leads" proto in the picture also has a 9 volt battery snap instead of the DC jack. In this manner, the wires can be laid flat onto the board giving a very low "in-line" profile that can be enclosed in heatshrink.

I'll have a bunch off to GadgetGangster soon and we will update the product page once he has them.

schill

I like the idea of covering the whole thing with heat shrink tubing.

Do you foresee any problems with heat dissipation?

WBA Consulting

It all depends on current draw, but I don't think the heat generated at the upper limits would be a problem under heatshrink.It would not dissipate heat as well, but unless you are continuously pulling a lot of current, it shouldn't be an issue. I have the PowerTwig for my PlungeLogger wrapped in heatshrink and it always stays at room temperature, but I think I am peaking at 120mA so that's not saying a whole lot.