Higher Amperage UBEC DC/DC Step-Down Buck Converter?

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j4mes
 
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Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

I'm building an LED hoop that needs 5A 6A ( 9A at white full brightness).

I am powering it with Li-Ion batteries at 7.4V.

This product is almost perfect, but it doesn't have enough amperage!
https://www.adafruit.com/products/1385

Does anyone know where I could get a 6A or more UBEC?

The kicker is that it needs to be 19 mm or thinner in order to fit in my hoop.

I have looked at Non-Isolated DC/DC Converters, but stand alone they require some fancy soldering which I am just not up to at the moment.

Thanks!

James

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

Depending on the circuit, you may be able to use multiple distributed UBECs to achieve the 6A. Can you post a diagram or more detail?

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

Heres my lil diagram.

I'm controlling 150 LPD8806 LEDs with a teensy 3.1 using an array of li-ion batteries to give me 7.4V.

Because of the size constraints of the hoop, I want to use as few components as possible.

I am also going to be cramming an IMU in here eventually so I also want to keep the weight down.

It looks the Adafruit UBEC is nicely prebuilt, and I'd like to avoid having to build one myself. But I guess if you want something done right... sigh..

Thanks!

James
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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

With 150 pixels, you should be feeding power at multiple points anyway. If this is a hoop, I would connect the power and ground where the start and end of the pixel strip meet. Then I would divide the 5v rail into 2 separate sections and use a UBEC to feed power to the center of each one.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

So do you mean supply power in 4 separate places or 2?

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

2 is probably OK. If you break the 5v rail into 2 sections of 75 pixels each, then feed power to the center of each of those sections, no pixel will be more than 38 pixels away from a power feed.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by waltr »

Look for higher current BECs from RC hobby suppliers.
A quick Google search found many such as this one:
http://www.helipal.com/8a-switch-mode-u ... OgodfgMA0g

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

Look for higher current BECs from RC hobby suppliers.
Even with a higher current BEC, you should feed power at multiple points if you are driving 150 pixels.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

Ah okay I get it now. So in theory if I hook up two of these ubecs in parallel I'll have 6A total to work with?

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

Sort of. It is not a good idea to directly connect power supplies in parallel. But if you separate the 5v lines into 2 segments as described above, each UBEC will be powering only half the strip.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

Right right, of course, I'm going to give it a shot! Thank you :)

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

I'm having the hardest time finding a SPST switch suitable for this project.

It needs to handle 7.4v and 6+ amps... Preferably push-button or toggle... What should I be looking for?

Otherwise the other option is putting the Teensy into sleep mode, but that won't completely cut power.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

Since you have 2 UBECs, you could use a DPST (Or A DPDT and ignore the extra terminals)
Otherwise the other option is putting the Teensy into sleep mode, but that won't completely cut power.
If you can get the Teensy to turn off the LEDs, the current will be lower for switching.

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by j4mes »

I'd really prefer to cut the power at the batteries, before it gets to the buck.

Do I really need to worry about the amperage ratings of switches?

I guess if the answer is yes, my best option will be putting the teensy in sleep mode.

Thanks again Bill!

James

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Re: Higher Amperage UBEC DC/DC Step-Down Buck Converter?

Post by adafruit_support_bill »

Switch ratings for DC current usually pertain to the life of the switch contacts. Making and breaking a DC circuit creates arcing between the contacts which can cause them to degrade over time. You should be able to find automotive switches with suitable ratings. Or get a multi-pole switch and wire all the poles in parallel to increase the current capacity.

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