A Question of Power

I'm currently working on an alarm clock project. The clock will be a perspex cube with the face being 24 leds in two rings for hours and minuets and one more for pm indication.

I'm currently concerned about power constrains and could do with some guidance if anyone would be so kind.

The brains will be an Uno R3 powered by an unregulated 7.5v 1a DC supply.
In addition...
1 x MPU-6050 gyroscope
25 x 3mm 5v 20 mA LEDs
2 x Sparkfun TLC5940 breakouts
1 x 5528 light sensor breakout
2 x sets of IR led and phototransistor 25mA
1 x DTS1307 AT24C32 RTC
And a buzzer of which I have not decided on yet.

The TLC5940 boards will be driving the leds.

My question is, will the Arduino handle all of that? If not could I use a second 5v regulator off the VIN to power the TLCs leaving the Arduino to handle the rest. If so, I've found a tiny breakout that has a V+ and gnd for both in and out, where does the ground in come from?

xn1ch1:
25 x 3mm 5v 20 mA LEDs
2 x sets of IR led and phototransistor 25mA

...will the Arduino handle all of that?

Probably. The UNO's regulator is a 7805, I believe ncp1117st50t3g, which should be able to provide up to 1A in theory, although better to stay well away from the limit. If all 25 LEDs and the 2 IR LEDs are all on at once, this would dominate the current needs and be 500~600mA. The other components will probably need a few mA each.

xn1ch1:
could I use a second 5v regulator off the VIN to power the TLCs leaving the Arduino to handle the rest.

Better to have a separate connection to the DC supply, to avoid overloading the UNO's PCB track.

xn1ch1:
If so, I've found a tiny breakout that has a V+ and gnd for both in and out, where does the ground in come from?

From the -ve connection on the DC power supply. All grounds should be connected together in your project.

Sounds like a very "different" alarm clock. What to the gyros and IR leds do?

Paul

Thank you for the reply. So I should be ok for power off the arduino? I'm hoping to keep it as one power input to keep it clean looking.

The IR setup will be in the bottom and top. In clock mode the top detects proximity to turn the alarm on and off and to silence the alarm when running and the bottom remains dormant. They will be configured in a way to make it seem that the perspex is being pressed.

When placed on its left side (gyroscope) the clock enters alarm edit mode where the now left and right IR sensors allow change of the minute and hour values. The same happens with the clock on its right hand side. This allows the clocks time to be edited. With some fancy animation to signify different modes

The lights sensors job it to pass ambient light values to the Tlc to dim the clock face in the dark.

To detect orientation of the cube I would have thought you want a three-axis accelerometer rather than a gyro.

I would definitely use another regulator to supply the LEDs. THe big issue is the onboard Arduino regulator is Linear, which means the more current it draws, the more power it burns off as heat. This means it can get really hot with large currents, and the 1A rating doesn't quite say how much heat-sinking it needs to work at that, and the Arduino's regulator's heat-sinking is limited, since its just mounted to some copper on the board. A better idea would be to have either an external switching supply to supply power, multiple LDOs, or a switching regulator. Pololu sells switching regulators for $5-7 Pololu - Regulators and Power Supplies. Just make sure you get one with enough current.
You can still run some stuff off the Arduino's regulator, but you should at least run the display LEDs from an external regulator/supply.

I've ordered a 3 axis accelerometer, I assumed that's what a gyroscope was.

Could I feed a second regulator via the pins underneath the jack?

xn1ch1:
I've ordered a 3 axis accelerometer, I assumed that's what a gyroscope was.

Could I feed a second regulator via the pins underneath the jack?

Assuming they connect to the Jack, sure, that should work fine. I'd just do a continuity test first so you know what is what.

xn1ch1:
I've ordered a 3 axis accelerometer, I assumed that's what a gyroscope was.

That's the right answer. An accelerometer detects acceleration in a given direction. If you have three of them covering all three axes, and they're attached to something which is essentially stationary, you can use this to work out the direction of gravity which tells you which way is 'up'.

A gyro is used to detect rotation around an axis, which is no help to you here.

Thank you again for your help with the power issues. I though I would report back and let you know of my success.
I used some right angle header pins to create a fixed pin output on the arduino dc jack to a small capacitor and regulator on a proto board above. All works very well.

I’ve attached pictures. On the dc jack the two middle pins are placeholders connected to the third pin on the jack as support only.