Please note: Friday June 18 is a holiday celebrating Juneteenth, please allow extra time for your order to arrive and plan accordingly.
0

Powering LEDs and HR-sr04 for Covid hat
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Powering LEDs and HR-sr04 for Covid hat

by TechLadyCC on Mon Feb 08, 2021 10:48 am

I need some help and thought I would start here. Can you help me figure out the right way to power this circuit? It actually works, but gets wonky because the power is insufficient. I also don't like to experiment with electric circuits - especially in a wearable.

I have a student who has made a Covid-19 Social Distancing Hat using an Adafruit Flora, Arduino code, 3 RGB LEDs (lilypad pixel boards) and a HR-sr04 sensor.

Here is a pinout diagram for the FLORA: https://pighixxx.tumblr.com/post/567140 ... ora-pinout
Here is a data sheet for the pixel boards: https://cdn.sparkfun.com/datasheets/E-T ... el_v11.pdf. They are sewn in series.
Here is a data sheet for the HR-sr04: https://cdn.sparkfun.com/datasheets/Sen ... HCSR04.pdf

I can get a LiPo battery with a JST connector to run the circuit (https://cdn.sparkfun.com/datasheets/Sen ... HCSR04.pdf). I have connected the HR-sr04 to VBatt. However, the Ultrasonic sensor needs 5V (I've discovered) to work properly. I am totally not good at figuring this out, but I wonder if I hook up the Flora to an adequate battery, if I can run the USS to the VBATT pad* on the flora. I see that all lipo batteries are ~3.7v-is this a place a booster would be appropriate? Or, I was wondering if I should hook up the HR-sr04 to an external battery (again what size?) I read somewhere that you can do this, but must ground it in a special way.


*From the adafruit Flora info "The most commonly confused part of the Flora is the VBATT pad and how power management is handled in the Flora. We designed the flora to be mainly powered via the JST connector. You can power it with a battery pack or lipo battery. That input is polarity protected and also controlled via the on/off switch. The battery output after the switch is VBATT. You shouldn't use VBATT as an input as you might damage your battery if you also plug in the USB connector to a computer! The ideal use of VBATT is when you want to power something like NeoPixels or a servo, something that requires more than the 150mA available from the onboard regulator."

2021 is my year to finally add understanding this to my skillset. In the meantime, any advice?
Thanks!!

TechLadyCC
 
Posts: 3
Joined: Mon Feb 08, 2021 10:29 am

Re: Powering LEDs and HR-sr04 for Covid hat

by adafruit_support_bill on Mon Feb 08, 2021 11:13 am

The Flora can handle battery input voltages up to 16v. A 3x Alkaline pack would provide 4.5v which is probably close enough to 5v for your sensor. A 4x battery holder with rechargeable NiMH cells (e.g. Eneloop) would be 4.8v which would almost certainly work. We have 3x holders with JST connectors
https://www.adafruit.com/product/727

A boost converter would be an alternate solution. The PowerBoost 500 Basic should have plenty of power for your project: https://www.adafruit.com/product/1903
The PowerBoost 500 C also has a built-in charger: https://www.adafruit.com/product/1944

adafruit_support_bill
 
Posts: 81308
Joined: Sat Feb 07, 2009 10:11 am

Re: Powering LEDs and HR-sr04 for Covid hat

by TechLadyCC on Sat Apr 24, 2021 12:22 pm

Thank you for this Bill. The student in question does not want to mount a large battery pack to the hat so we are going the route of the Power Boost. I have a Power Boost but am wholly uncertain as to how to wire it up to the FLORA. We have Pins 6, 9 and 10 devoted to LEDS and the HR-sr04....unsure how to wire the power and ground. Can I hook the Power Boost to the FLORA with a USB/USB mini cord? and then the battery connected to the power boost?I appreciate the guidance!!

Also, in terms of mAh for the 3.7v lipo battery. What value should I have?

Thank you!!

TechLadyCC
 
Posts: 3
Joined: Mon Feb 08, 2021 10:29 am

Re: Powering LEDs and HR-sr04 for Covid hat

by adafruit_support_bill on Sat Apr 24, 2021 1:31 pm

Can I hook the Power Boost to the FLORA with a USB/USB mini cord? and then the battery connected to the power boost?

Yes. That will work.

Also, in terms of mAh for the 3.7v lipo battery. What value should I have?

To drive a Flora, HC-sr04 and 3 pixels, one like this should handle the load: https://www.adafruit.com/product/2750

adafruit_support_bill
 
Posts: 81308
Joined: Sat Feb 07, 2009 10:11 am

Please be positive and constructive with your questions and comments.