PDA

View Full Version : 5V step up converter needed for driving Teensy + WS2811



neep
02-08-2013, 10:40 PM
I've been working on an LED toy for a while now, using a WS2801 strip getting me 48 pixels. I am using around 350-400mA at 5V including powering the Teensy 3. My power is a couple of li-ion 10440 cells in parallel, so 3.7V, around 1200mAh. The 5V comes out of one of these boost converters: https://www.sparkfun.com/products/10255

I opted for that one as I needed something really small and it could deliver the amount I needed. Now I want to start using a WS2811 strip, to double my pixel count to 96. Obviously I'm going to be drawing more power, around 700-800mAh.

So I'm looking for a boost converter that is a little more powerful, but hopefully not much bigger. I've been googling like mad but can't find anything useful that I can buy off the shelf. Any ideas here for what would be a solution? I've looked at building my own circuit, but every which way I try I'll never get it as small as those factory made SMD boards.

Jp3141
02-08-2013, 11:24 PM
Try this: http://www.ti.com/lit/gpn/ptn04050c

Qumefox
02-09-2013, 06:04 AM
What brand 10440's are you using? My experience with Li-ions (I build handheld lasers as a hobby) has shown me most 10440's are only good for 300-400mAh at best.. the ones the claim 600 are usually lying.

Just something to keep in mind when you start upping the current draw.

neep
02-09-2013, 09:44 AM
Qumefox: I'm using the Ultrafire / Trustfire ones and they indeed are only around 300mAh. But I'm using 4 of them, so that gives me around 1200mAh altogether. I can fit some more in if needed. An hour's worth of burn time is enough for me.

Jp3141: thanks for that, it looks really good, with 2.4A at 5V, wow. And it is small, but not small enough. The max height is 12mm, which is more than I can afford to pack inside my toy. I need it to be around half of that height. The board can be a little wider and longer, but that big block sticking out is going to be a problem.

And it's too powerful for my needs actually. Something that can do 1A @ 5V would be perfect.

What I do like about the Sparkfun LiPower modules is that they have an under-Voltage lockout function, so that they shut down around 2.7V, to protect the batteries. I don't require this, but it's a nice to have.

I've also considered running it with the native battery Voltage, but then I'd be looking at LEDs that aren't consistently colored, and possibly the Teensy will stop working when the Voltage drops below 3V.

hpyle
02-09-2013, 02:28 PM
This one is the smallest all-in-one 1A booster I've found -- I haven't measured whether it's really capable of 1A, but it works OK for me.
http://www.hobbyking.com/hobbyking/store/__11784__TURNIGY_Voltage_Booster_for_Servo_Rx_1S_t o_5v_1A_.html
Dimensions are 20 x 9 x 15 mm. The board is ~20x12 and the caps overhang by a few mm-- it's probably possible to resolder them to get the width down.

Jp3141
02-09-2013, 02:32 PM
Would you have room to put two in your system ? You might be able to parallel them (not generally a good idea, but it might work), or you could run half the lights from each (i.e. each runs from the LiIon, but the outputs are separated) - ground would be common and you can still run from the same control.

hpyle
02-09-2013, 02:36 PM
Ooh. I like the look of that TI part.

Qumefox
02-09-2013, 04:51 PM
Would you have room to put two in your system ? You might be able to parallel them (not generally a good idea, but it might work), or you could run half the lights from each (i.e. each runs from the LiIon, but the outputs are separated) - ground would be common and you can still run from the same control.

Very very bad idea.. Generally boost drivers have to be specifically designed to be able to run in parallel.. And I can tell you.. very very few are. Trying it usually only results in the drivers losing their magic smoke.

I actually know of a boost/buck inverter that'd be almost perfect for neep's needs save one major flaw.. It's a constant current driver meant for driving laser diodes, instead of constant voltage. But otherwise, it'd be perfect since it's 4mmx9mmx12mm and will do 2-5.5v and up to 1.5A off a single Li-ion.

Jp3141
02-09-2013, 05:13 PM
Very very bad idea.. Generally boost drivers have to be specifically designed to be able to run in parallel.. And I can tell you.. very very few are. Trying it usually only results in the drivers losing their magic smoke.


I looked at the Sparkfun device -- it doesn't have output current limiting, so you can't parallel their outputs reliably (it won't blow up, but the output won't be stable as you exceed one device's current capability).

You can still use two of them (parallel inputs) and have separate outputs for two LED strings. Remember to keep the two 5V outputs separate -- both on the converter and the LED strings.

neep
02-09-2013, 07:17 PM
Jp that would not be practical. Already I have been thinking over the wiring quite a bit to make it as efficient as possible and I can't really afford another power line running through the tube with the batteries in there as well. The problem is also that the Sparkfun part is quite expensive and I've already managed to blow up 2 and I got 1 DOA, so I'm not that impressed and would be weary of doing any tricks with them.

hpyle that looks very interesting especially for that price! And it's made with flexible PCB, even nicer. I'm going to order a bunch of them. Thanks!

Russ
02-11-2013, 02:02 AM
Hello, newbie here but I have been looking for a similar solution, has to go inside a tube too. I found this http://www.ebay.com/itm/1-PCB-Li-ion-Lipo-Battery-3-7V-step-up-Convert-to-Output-Power-DC-5V-DLX-UPDC5V-/251115596858?pt=LH_DefaultDomain_0&hash=item3a77a7ec3a and am thinking of grabbing one to try out. It is small enough (40mmX10mm) and is supposed to be battery protection and a booster. I do not know what the amperage coming out is though.

If I get one I will let you know how it does.

neep
11-01-2013, 02:35 AM
Hi again. I'm back from a break on my LED projects and I have only just now ordered the part that hpyle pointed me to, but I am also having some success with some of the the Pololu range that I have tried so far:

http://www.pololu.com/search/compare/133,132,133,132/0,s,8,1,21,22,50,100,99,108/130,33,107/x

I'm still experimenting as to what is the best for what I need, and I will update here, but I just wanted to point people to their range of products in case anyone else is looking for a good selection of (adjustable) step up/down power converters that are also quite small.

Jp3141
11-02-2013, 06:00 PM
neep -- be a little cautious -- some of these products list the input current, not the output current. The output current will be something less than
INPUT_current*INPUT_voltage/OUTPUT_voltage

neep
11-03-2013, 12:12 PM
Yeah - I am not expecting miracles, but for the price of these modules I'm willing to experiment. I've ordered a number of them and will let y'all know how it goes and which ones work best for me. If I can squeeze 500mA at 5V out then I'm happy. The Sparkfun converter is not able to deliver this to begin with, and its output voltage drops dramatically plus it starts making "coil" noise when I draw too much. I already broke a few. They are quite pricy so I'm done with those anyway. I've ordered these:


Pololu Step-Up 5V 600mA Voltage Regulator U3V12F5 (for the project mentioned above)
Pololu 5V / 1A output Step-Up/Step-Down Voltage Regulator S7V7F5 (another option)
Pololu Step-Up/Down 2.5-8V 1A Voltage Regulator S7V8A (for general 3.3V - 5V use)
Pololu 3.3V Step-Up/Step-Down Voltage Regulator S7V8F3 (for driving blue LEDs directly)
Pololu 12V Step-Up Voltage Regulator U3V12F12 (for driving 12V LED strips)

markvr
11-07-2013, 09:00 PM
Why not put the LiOn cells in series, and then drop the voltage? There are probably more regulators around that can drop the voltage than boost it? Or have I missed something? Seriously, I'm about to build something that does this, so if I've missed something tell me!

neep
11-08-2013, 08:15 PM
markvr: I thought about that, but it is not an option for me as I would then not be able to charge the batteries simultaneously. This is far easier and safer when they are in parallel. When going in series the voltage needs to be exactly right or I risk blowing up cells, and the relatively simple Li-Ion chargers that I use are not able to do this. Building my own charger isn't really one of my goals.

With some switches it could be possible to alternate between parallel for charging and series for operating, but that would involve running more wires, and space and weight is at a very high premium in these projects. Every cubic millimeter matters.

BTW I am having reasonably good success with the S7V7F5 so far. I am able to squeeze a peak of 600-700mA out with a drop to 4V when the batteries get towards empty. Not bad. As long as V stays above 3.5 the Teensy 3 is still running. I think I may stick with this one as I like the 2.7V drop-off, giving my (protected) batteries an extra protection.

markvr
11-08-2013, 11:49 PM
ah I see, I don't have that problem because I remove the batteries and put them into a standalone charger. I also need about 10amps, and there aren't that many regulators around that can manage that!

neep
11-09-2013, 11:30 AM
Right. My 10440 batteries are very tightly packed into an aluminium rod with soldered wires just barely fitting right next to them. I really want to avoid having to take them out of access them in any other way. All I want to do is plug them into the charger with a DC jack. My power needs are fortunately a bit more modest than yours! I last about 2 hours now on 4 x 10440 li-ion "AAA" batteries, but it depends on the program. This is the current program:

http://www.youtube.com/watch?v=sLXNJJdvkBo

Jp3141
11-09-2013, 04:47 PM
Did you check what voltage the LED strip actually needs ? Perhaps it will run directly down to 3.7 V ? I think the Teensy will also.

neep
11-09-2013, 09:42 PM
The LED strip wants 5V but can do with a little less. If the voltage drops below 3.3V the Teensy will start to cause lots of noise on the data line, resulting in erratic behavior of the LEDs. Also the color will start shifting to red as that tends to be able to do with lower voltage.

I really don't want this to happen. When I am doing a show the voltage needs to stay high enough until the very end.

But really, this is a solved problem with the Pololu boost converter module I'm using now. Very happy with the result. A year ago I couldn't find these things, perhaps they didn't exist yet. But now they do, and I can recommend them.