Power Supply Design for Propeller

Timothy D. Swieter

I am toying around with a few ideas and applications for the Propeller.· One of the ideas is a generic button/LCD interface.· I have a thread in the sandbox forum where I am exploring and designing the concept further.

http://forums.parallax.com/showthread.php?p=736828

For this idea, and my other ideas, I want to explorer the power regulation circuitry more.· My past designs used the LM1086s just like the Propeller·Protoboard.· This works well, but not under the constraints I would like for the new design.· I would like a power system that

• Can accept 6 to 12V DC input - maybe up to 24V DC
• Doesn't require a heat sink
• Minimal components (isn't this always a constraint?)
• The component packages should be SMT, but hand solderable
• 3.3V DC and 5V DC output

I am thinking the design will have to be some sort of DC/DC switching regulator in a buck mode format.· What thoughts or suggestions do you have?· Anyone done something similar already?

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Timothy D. Swieter, E.I.

www.brilldea.com·- Prop Blade, LED Painter, RGB LEDs, uOLED-IOC, eProto fo SunSPOT, BitScope
www.sxmicro.com - a blog·exploring the SX micro
www.tdswieter.com

Peter Verkaik

On my latest boards I used dc/dc regulators from Recom:
http://www.recom-international.com/switching_regulator_R-78xx.html

Not cheap, but when you realize you don't need any heatsink, the low profile
and small board space, just a perfect component. They even have a 1A smd version.

Two links to datasheets are at the bottom of the page.

regards peter

Leon

Have a look at the Simple Switcher chips from Nat Semi. This will probably do what you want:

http://www.national.com/pf/LM/LM2675.html

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Timothy D. Swieter

Thank you for these suggestions guys. I have done some searching on my and but I didn't cross these two particular products. I will read more about them in the coming days. At first glance the LM2675 looks promising. I could use that to regulated the incoming voltage to 5.0V and then perhaps use another one to regulate to 3.3V or maybe use some other chip.

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Timothy D. Swieter, E.I.

www.brilldea.com·- Prop Blade, LED Painter, RGB LEDs, uOLED-IOC, eProto fo SunSPOT, BitScope
www.sxmicro.com - a blog·exploring the SX micro
www.tdswieter.com

MagIO2

I like the on/off pin on the SMD version of the Recom regulators. You can have power subsystems which are switched on and off by the Prop as needed. E.G. as a "screensaver".

Mike Huselton

Tim,

I have been using the Simple Switcher series for 7 years. The physical board layout is important, as is choice of inductor.

The sample printed circuit board assembled by National engineers to provide a complete reference design is in my hand.
The complete board is 1 inch by 1/2 inch. It provides 1 amp at 5v.

I can mail it to you if you PM me to provide mailing details for your complete address.
Is it all right to re-use the mailer that you sent me?

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JMH

Post Edited (James Michael Huselton) : 3/19/2009 7:34:37 AM GMT

Timothy D. Swieter

Ha - this thread is old, started back in July. It looks like MagIO2 kicked it back up. The funny thing is earlier this week I said I need to get back to this design and finish it! Maybe this is all a sign.

Thanks for the offer James, at the moment hold on to it. I am interested in seeing it, maybe you can post pictures? I am saying don't send it because I am doing lots of traveling in the next couple weeks and I may also be relocating to Singapore. So, anything sent in the mail at this point I may not get depending on schedule.

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com

Post Edited (Timothy D. Swieter) : 3/19/2009 8:41:48 AM GMT

kenmac

Tim,
Futurlec (Thailand) have a range of what they call Mini- Boards.
Among the range are some ready built , LM2575 based, regulator boards.
You can see them here
www.futurlec.com/Mini_Power.shtml
Prices are $US, and seem to be quite reasonable.

kenmac

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Perth, Western Australia
Time Zone = GMT + 8

Peter Jakacki

I have a standard module which I use based upon the LM2594 or LM2675. The standard chip I use is the 2594 rated at 0.5A. I include a small SOT-23 LDO regulator for the 3.3V rail which is good for about 200ma. The module has extra pins to trim the +5V and also turn the 3.3V rail off.

The only real difference between the two switching chips is that the 2675 runs at 1A and a higher frequency so that it needs a smaller inductor (although the 100uH works for higher voltages). I allow for the extra little bootstrap cap that the 2675 requires whereas that pin is a 'not-connected' on the 2594 so it doesn't hurt.

I keep a few of these in my little protoyping parts box as they come in handy at times.

*Peter*

Cluso99

I used the LM1117 in TO252 with the TO220 pins in between on the TriBladeProp. Neither are switchers.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBladeProp, SixBladeProp, website (Multiple propeller pcbs)
· Prop Tools under Development or Completed (Index)
· Emulators (Micros eg Altair, and Terminals eg VT100) - index
· Search the Propeller forums (via Google)

My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Jimmy W.

1 recommendation that I have found super useful over and over, just after your input plug, put a fullwave rectifier followed by a 50v(for a circuit whose max voltage is 24vac/dc) cap, that way if someone feeds it wrong polarity DC or even AC you are OK. It only adds penny to the cost but adds lots of flexibility.

Cluso99

I just use a 1N4004 diode (only 1 voltage drop and little space). I agree, some protection is good. I use a 100uF 35V Electrolytic. My circuit fits in 0.4"x2.9" on the TriBladeProp. And a slide switch is good too.

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBladeProp, SixBladeProp, website (Multiple propeller pcbs)
· Prop Tools under Development or Completed (Index)
· Emulators (Micros eg Altair, and Terminals eg VT100) - index
· Search the Propeller forums (via Google)

My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

mctrivia

I have built a 97% efficient 3.3 v dual source module. polarity protected with voltage input between 3.5 and 14 v parts costs makes it not cheap but the module is only 1 inch in size and works well.

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

Peter Jakacki

I agree with Ray concerning input protection. I just use a single diode and a 100uF 35V Electrolytic (or two). If you try to use a bridge rectifier then there may be a problem when other interconnected units are hooked to the same power as well because the "common" is no longer common.

*Peter*

Timothy D. Swieter

Last night I cooked up a DC/DC circuit using the LM2594. I did include a diode for reverse polarity protection. The attached schematic image isn't anything special, I followed the designs in the data sheet. Over the next week I will be doing a layout with the remaining portions of the circuit. This is for an LED controller product that uses the Propeller. In this product I don't need 5V, only the 3.3V so this is the only power supply. I will rate the product at max voltage of 16 or 17V, normal operation will be 12V.

Using these simple switchers in a design are pretty easy.

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com