Complete newbie, need help with component selection.

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Brian_Bragg
 
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Complete newbie, need help with component selection.

Post by Brian_Bragg »

Hey,

I'm looking for a bit of help with a project. I have a good list of requirements for what the finished project needs to do, but I'm running into issues figuring out if the components I'm looking at can actually drive the project, or of the whole thing would explode the moment I plugged it in, due to drawing two much current. I'm working within some fairly tight space constraints, so I will very likely end up having to have the final device built on a custom PCB, but right now, I'm just looking to put together a proof of concept level prototype using a 3v Protrinket and some break out boards. The thing is, I'm having issues figuring out if the break out boards can drive some of the components I need to work with.

The specs for the project are below.

9 Degrees of Freedom motion detection (3 axis Accelerometer and a 3 axis gyroscope).
4 PWM Output channels for LED's running at up to 3.2V and 20mA.
4 PWM Output channels for LED's running at 350mA and 3.1V (may see up to three of these LED's wired in parallel on each channel).
1 Channel Audio to drive a 2W 8Ohm speaker.
MP3, Wav, and Ogg Decoding.
MicroSD card for mass storage.
The Ability to write to and edit the MicroSD card in place through a microUSB port.
3.7 Volt Lithium Ion Battery power supply.

Currently, I'm looking at the following boards:
Adafruit Pro Trinket - 3V 12MHz - Brains of the device.
Adafruit 9-DOF Accel/Mag/Gyro+Temp Breakout Board - LSM9DS0 - for motion detection.
Adafruit 12-Channel 16-bit PWM LED Driver - SPI Interface - TLC59711 - for controlling the LED's
VS1053 Codec + MicroSD Breakout - MP3/WAV/MIDI/OGG Play + Record - v4 - for the Audio
And *maybe* Adafruit DRV2605L Haptic Motor Controller - because haptic feedback would be a nice feature to have, even if it's not critical.

They would be driving:
Up to 12 Cree XLamp XB-D Color LEDs
Plus 4 Additional LED's, and a 2 Watt 8 Ohm speaker.

Power Supply would be Panasonic Li-Ion 18650 3.7V 3400mAh PCB Protected Rechargeable Battery.

I know if I'm driving 12 of the high performance LED's battery life is going to be an issue, but I actually have a solution worked out for that. My main concern is whether or not I can run that many LED's without burning out the board itself.

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adafruit_support_mike
 
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Re: Complete newbie, need help with component selection.

Post by adafruit_support_mike »

You'd need power mosfets to drive the high-current LEDs, with the Servo Driver controlling those.

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Brian_Bragg
 
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Re: Complete newbie, need help with component selection.

Post by Brian_Bragg »

Mike. Thanks for the response. I'm assuming you mean the 16-Channel 12-bit PWM/Servo Driver The only issue I see is that the Servo board runs at 5 volts, and I'm working off a 3.7 volt power supply due to space limitations. I'm trying to catch back up, but honestly I haven't held a soldering iron in 23 years, so my skills are a bit rusty. How would I step up from 3.7 to five volts?

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adafruit_support_mike
 
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Re: Complete newbie, need help with component selection.

Post by adafruit_support_mike »

Yeah, you'll need something other than the TLC59711 to control 350mA channels. The mosfets we have in the shop will work, but so will just about any power mosfet, and the Servo Driver can run the mosfets.

If you want to run more than one 350mA LED per channel, give each one its own mosfet, and control those in parallel. No two LEDs have exactly the same forward voltage, and if you put them in parallel the one that operates at the lowest voltage will choke out the others.

To boost a 3.3v supply to 5v, you can use one of these: https://www.adafruit.com/product/1903 It's a fairly common request. ;-)

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Brian_Bragg
 
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Re: Complete newbie, need help with component selection.

Post by Brian_Bragg »

Thanks again Mike. I think my biggest challenge is going to be the space. The prototype can be a bit larger, but the final piece has got to be fairly tiny. I might end up stacking a pair of boards to fit everything in.

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