Requesting Help with Correct Sensor Selection for my Project

Good morning!

I'm creating a new product (sport/game) and after some research I've decided that I'd like to incorporate a few Arduino sensors inside of it. I've been learning all I can lately about Arduino, however I am in need of a little help with choosing which sensors to purchase. Below is a description of what I'm looking for:

  • Probably just the Arduino UNO is fine (I can handle this lol)
  • A light sensor that can detect current lighting levels. The goal here is to be able to receive readings on current lighting levels and then slowly begin to dim (ON) a strip of LED lights as the environment gets darker. Alternately, as the environment gets brighter, the LED strip lights would begin to fade until they are off completely. Besides pointing me towards this specific sensor, is there a way to extend the diode so that it doesn't need to be right at the Arduino board? The UNO will be inside the product at the centre, but I would need the sensor to be able to be mounted towards the surface in order to receive any light.
  • Second, I'll need an impact sensor (there's probably a more correct term for this...). When my product is hit or moved in any way, I would like those same LED light strips to flare up to full brightness for a short time. Is there a good sensor for this? An accelerometer or a gyroscope??

Thank you in advance for your direction!

An LDR would be a suitable light sensor. Connect it from an analogue input to gnd and fit a 10k pull up R to 5v.
The LDR can be positioned and connected to the Arduino via cable.

Depending on how sensitive you want the movement detector and how high tech, you could have a few tilt switches at various orientations that can be monitored.

Weedpharma

Thanks, I'll look into those. On another note, I'm now struggling with how to independently power my arduino... I'll only have the light sensor (or LDR), movement sensor, roughly 2ft. strip of LED lights and rocker switch connected to my UNO in the setup. Now, would I need a 6x AA battery holder to power this or can I do a rechargeable battery setup with a recharging chip and 7.2V or 11.1V li-ion battery pack? The rechargeable option is preferred, but would I need anything extra such as a 'moderator' or something that keeps used voltage at a constant level??

The uno has onboard voltage regulation so you can feed it with 7.2v safely (via power jack).

Weedpharma

I would start with 6-AA batteries and worry about rechargeable batteries when the prototype is working properly. Ditch Arduino UNO and replace it with a custom board to save power. If you're only turning on the LED when it's dark, you don't need much power to keep them bright against dark surrounding. All of those happen after you get a prototype to work first. For impact sensor, I recommend an accelerometer, such as ADXL345. You can sense impact, knock, tilt etc. If you want the light sensor against the device, hot glue it. Add more wires to the sensor to reach your arduino in the middle.

Hi,

The problem with most led strips is they require a 12V supply.

WS2812B led strips require only 5V, and have the advantage of the ability to display many colours and patterns. However, they are very current-hungry.

Paul

Thanks guys this is all very helpful. I'll post again if something else comes up, but this is great to get me pointed in the right direction :slight_smile:

PaulRB:
Hi,

The problem with most led strips is they require a 12V supply.

WS2812B led strips require only 5V, and have the advantage of the ability to display many colours and patterns. However, they are very current-hungry.

Paul

Paul,
I found an LED strip that is perfect for my application ( SENCART 7.5W 340lm Cold White 120-3014 SMD LED Waterproof Strip Light - Free shipping - DealExtreme ), and so I would like to try to use this with a rechargeable battery in the long run. I'm not very familiar with electrical components and terms, but I'd assume that because these likely require 12Vs, does that just mean that the 5Vs the Arduino will supply to them will just not allow them to be as bright? If so, what are my options and what would be the best setup?

This is the rechargeable battery I'm looking at: http://www.dx.com/p/7-4v-30c-1500mah-li-poly-battery-pack-for-r-c-model-silver-grey-165535#.Ve-TrGK9KSM

And this is the Charger: http://www.dx.com/p/mp1405-5v-1a-lithium-battery-charging-board-blue-black-219454#.Ve-PtWK9KSM

Thanks!

The LEDs need 12V because they are three LEDs in series with a current limit resistor.
Each group of three will need 20mA.
5V from Arduino would turn at most 1 LED from each group.
How much of the strip are you controlling with 1 signal? You need a transistor like AOI-514 to sink current thru the strip to turn it on, the Arduino output will control the transistor.
http://www.digikey.com/product-search/en?keywords=aoi514

Autumnslash:
I'd assume that because these likely require 12Vs, does that just mean that the 5Vs the Arduino will supply to them will just not allow them to be as bright?

No, leds don't work like that. They may not light at all, or as Crossroads says, you may be lucky and one led in three might light.

If you really want to use 12V strips with a battery that gives less than 12V, then you could use a "step-up convertor" like this one for example.

Hmm, I see... Would this work?: A recharging module to an 11.1V battery pack, the 11.1V battery pack to the Arduino AND a voltage step-up boost module (bringing it to at least 12V in that direction), the booster to a relay switch, and then the relay switch to both the 12V LED light strip and the Arduino?

The battery pack to the Arduino should be fine because of the built-in regulator, and the Arduino to the relay switch (via analog) would allow communication for controlling how much power is being given to the LEDs (for dimming purposes).

If that's sorta hard to follow, I apologize. maybe sketch it out quick as you're reading it :stuck_out_tongue: But would you see any hiccups with that setup?

Thanks! I appreciate the feedback while I sort this out.

That should work, except for the relay.
Use N-channel MOSFETs to control the on/off time of the LED strip for dimming.
AOI514 or comparable part logic level gate, low Rds, low input gate capacitance part.
http://www.digikey.com/product-search/en?keywords=aoi514
Here’s an example of one of my board offerings with AOI514 driving 8 sections of LED strips

Ok, I'll research N-channel MOSFETs next. Here's a quick little sketch of my above layout, but if a relay isn't the right thing there, I'll check out the MOSFET as a replacement for the relay?

Sorry the photo was too large for above message. Here it is again…

http://www.digikey.ca/product-search/en?vendor=0&keywords=AOI514

Is this AOI514 MOSFET semiconductor (as per recommendation) the correct one for my application? It says 30V, but is that just its capacity? I just want to make sure it's not overpowered :slight_smile: Price point looks good, and if it's the missing puzzle piece to complete my above setup then I'm all for it. Does it simply go in place of the relay I've shown above?

12V goes to the + of the LED strip, - goes to the MOSFET Drain. MOSFET Source connects to Gnd.
Arduino connects to MOSFET Gate thru a 150, 220, 270 ohm resistor.

You're only switching 12V, the part can handle 30V. It's one of the lowest cost, very low Rds MOSFETs in a thru hole package.

If you're using Lithium battery, you need a charge counter to make sure you're discharging the battery too much. As far as I know, it's hard to find one charge counter that works around 12V range on a break out board for arduino. You can also estimate stored energy with battery voltage but that's a very crude estimate.