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dragonfruit35 wrote:

ScottMaurer19 wrote:

daydreamer0023 wrote: Something came up from tryouts and I wanted to clarify.

I mean technically an LED generates heat but its not very apparent

So do you think that the ES will actually measure to see if it heats up? I mean, light=heat so in that regard they must be exothermic.

I could see some ES being skeptical on how exothermic an LED is... One of the main featues of LEDs is that produce light without very much heat generation.

ScottMaurer19 wrote:

dragonfruit35 wrote:

ScottMaurer19 wrote: I mean technically an LED generates heat but its not very apparent

So do you think that the ES will actually measure to see if it heats up? I mean, light=heat so in that regard they must be exothermic.

I could see some ES being skeptical on how exothermic an LED is... One of the main featues of LEDs is that produce light without very much heat generation.

Totally agreed. Why don't you just buy some incandescent light bulbs - in incandescent bulbs, the light is generated because a wire has heated up, making them definitely fulfill the Exothermic->Light requirement? Digikey sells some with the same form factor as LEDs for $0.63: https://www.digikey.com/product-detail/ ... ND/3151432

Iwilsonp wrote:

ScottMaurer19 wrote:

dragonfruit35 wrote:
So do you think that the ES will actually measure to see if it heats up? I mean, light=heat so in that regard they must be exothermic.

I could see some ES being skeptical on how exothermic an LED is... One of the main featues of LEDs is that produce light without very much heat generation.

Totally agreed. Why don't you just buy some incandescent light bulbs - in incandescent bulbs, the light is generated because a wire has heated up, making them definitely fulfill the Exothermic->Light requirement? Digikey sells some with the same form factor as LEDs for $0.63: https://www.digikey.com/product-detail/ ... ND/3151432

Yeah, that was my plan, I've already found some ! I was just wondering since that seems to be a valid argument.

Would we have to use light bulbs? Couldn't we use calcium chloride or something?

tinyperson wrote:Would we have to use light bulbs? Couldn't we use calcium chloride or something?

If the reaction is exothermic, produces light, and won't put you in the hospital, it should be fine.

Could we use a phototransistor for this task, or does it have to strictly be a "photocell"

Hey -

so I'm pretty new to Arduino and the likes but I'm trying to use it for most of my tasks. I'm also going after battery bonus - so 12v is powering both the Arduino and everything else. Basically for this task I've got 12v wired to a 12v halogen light and am using a MOSFET and the Arduino to power it on/off. Problem is, the light comes on very slowly and the MOSFET begins to overheat. I measured the voltage across the bulb and it slowly climbs from 0 up; I stop powering it because I'm afraid I'm destroying the MOSFET. If it's any importance at all, the bulb is 50w (too much?).

I've looked online but can't solve my problem. Is the voltage at the gate too low? Everything else besides the Arduino is off at the time the light is turned on.

Thanks!

Edit: just measured the voltage at the gate and it's 5v, so it should be fine. I can provide a (poor) diagram if needed.

SluffAndRuff wrote:Hey -

so I'm pretty new to Arduino and the likes but I'm trying to use it for most of my tasks. I'm also going after battery bonus - so 12v is powering both the Arduino and everything else. Basically for this task I've got 12v wired to a 12v halogen light and am using a MOSFET and the Arduino to power it on/off. Problem is, the light comes on very slowly and the MOSFET begins to overheat. I measured the voltage across the bulb and it slowly climbs from 0 up; I stop powering it because I'm afraid I'm destroying the MOSFET. If it's any importance at all, the bulb is 50w (too much?).

I've looked online but can't solve my problem. Is the voltage at the gate too low? Everything else besides the Arduino is off at the time the light is turned on.

Thanks!

Edit: just measured the voltage at the gate and it's 5v, so it should be fine. I can provide a (poor) diagram if needed.

What mosfet are you using?

Also, since you just need to turn it on and off, if you cant get a mosfet to work, a simpler option may be a relay.

IRF520.

I tried relays, but either mine were defective, or I didn't wire them properly. Since the next invites are soon, I got rid of them for now - maybe later.

I am considering just using LEDs instead of the halogen bulbs. Anyone do the same and run into problems with this at competition?

Look at the first graph on page 3 of the datasheet for the mosfet you are using. https://www.vishay.com/docs/91017/91017.pdf. The arduino (assuming you dont have a 3.3v one) outputs 5v, so the gs voltage is 5v when the arduino pin is on. That (and i'm not 100% sure on the terminology here) should only allow about 2A to flow through the mosfet. If the bulb is 50w, it wants to draw about 4.5A, and possibly more when it is cold and first turning on. A solution could be to use two mosefets in parallel, or to get a mosfet with different characteristics. Or you could probably get a cheap incandescent bulb that uses much less power and not have to worry about whether a led is truly exothermic, like these:

https://www.amazon.com/Pack-Miniature-S ... 7045648011

Or, I would reconsider a relay: if you get one with a board, they are pretty easy to use. Something like this:
http://www.microcenter.com/product/4763 ... lay_Module

They have three pins, one goes to arduino 5v, one to arduino gnd, and one to the arduino output pin.