NTC available!!

[SafetyBob]

Just checking today for boring bar holder and checked Newark to see if they had any Ametherm SL12 1R010 NTCs. 400+ available as of now. Get them while they are available.

Bob E.

 

[LuxLuthor]

Indeed.

 

[SafetyBob]

Crap, I guess you must have seen them available a couple of days ago. I think the last time I checked was around 7 to 8 days ago.

Can't wait to get mine!!

Bob E.

 

[willrx]

Please help me. What does NTC stand for? Thanks.

 

[LuxLuthor]

Bob, actually I placed an order with Newark about a month ago....so they filled my backorder.

Will, it is an excellent question. Technically NTC stands for "Negative Temperature Coefficient." Aren't you glad you asked? LOL! In a simple explanation, these are like the "surge protectors" that you plug your computer into.

The first few sentences at Ametherm's web page here is a simple description that even I can understand.

The NTC Thermistor starts out as a relatively high resistor device that serves to block the intial spike of turn on current. The initial current spike hits this NTC resistor like a brick wall, and heats it up very quickly, thereby dropping its resistance to nearly insignificant.

Once that initial current spike heats up the NTC, its resistance drops, and the current continues through the circuit...but after the NTC took the brunt of the initial startup spike, which otherwise would have slammed the bulb filament.

Now, when I install my NTC, I want the current flow to hit it first, then the bulb filament. Because current flow was incorrectly named back in the days before they knew about the structure of the atom and electrons...there was a standard established that current flows from "Positive" terminal to "Negative." In reality, current flow is the movement of electrons from the "Negative" (bottom of battery) to the "Positive" (top of battery).

So I put my NTC in series either between the bottom of the battery and spring/body contact, or between the Bipin "Negative" wire and where it makes contact with side aluminum ground.

 

[willrx]

Lux,
Thank you Sir. I appreciate the explanation and your candor.:thumbsup:
May I ask how does one judge the "strength" of the NTC, or how to know if you've chosen the correct one for the job?

 

[LuxLuthor]

Lux,
Thank you Sir. I appreciate the explanation and your candor.:thumbsup:
May I ask how does one judge the "strength" of the NTC, or how to know if you've chosen the correct one for the job?

Well now you are getting on the "skinny branches" of my education of these NTC's. The honest answer for me personally is people who eat & sleep electronics and know about the fine points picked the model we are using in this topic. After I was drawn to it because of the experts picking it for us, I looked at the various amp rates listed on this link, and knew we needed between 6-12 Amps with the bulbs we are using.

I next saw that if you look at this particular data sheet, that it has a very low resistance once it reaches its 100% heated up level (0.027 Ohms) vs. the ones above and below it on previous link have a higher final resistance (0.04 Ohms). The next category of SL15 have an even higher final resistance (0.06 Ohms). You can use Ohms Law (V=IR) to see the effect of various levels of resistance on delivered bulb voltage at these current levels.

For example once the NTC is fully heated up and has a resistance of 0.027 Ohms being used in a 5761 bulb that draws 5.5 Amps, then

V = 0.027 Ohm x 5.5 Amps
V = 0.15 Volts dropped accross that resistor once heated up -- which is pretty minor.
​

Before the NTC is heated up it has a resistance of 1 Ohm, so it looks like this:

V = 1.0 Ohm x 5.5 Amps
V = 5.5V that drops accross the "cold" NTC...blunting the spike.
​

So all I know is you need one that can take the Amp rates we are using, an initial resistance strong enough to blunt the spike, a final resistance low enough to not diminish the current delivered to the bulb.

There is a way to determine the energy rating that is discussed here, but I'm not that advanced in understanding how to use that factor in picking the correct NTC yet.

 

[Ctechlite]

Now, when I install my NTC, I want the current flow to hit it first, then the bulb filament. Because current flow was incorrectly named back in the days before they knew about the structure of the atom and electrons...there was a standard established that current flows from "Positive" terminal to "Negative." In reality, current flow is the movement of electrons from the "Negative" (bottom of battery) to the "Positive" (top of battery).

So I put my NTC in series either between the bottom of the battery and spring/body contact, or between the Bipin "Negative" wire and where it makes contact with side aluminum ground.

I don't think it actually matters where you put it in relation to the bulb, positive side or negative, as long as it is in series with the bulb you are good to go.

 

[willrx]

Well now you are getting on the "skinny branches" of my education of these NTC's. The honest answer for me personally is people who eat & sleep electronics and know about the fine points picked the model we are using in this topic. After I was drawn to it because of the experts picking it for us, I looked at the various amp rates listed on this link, and knew we needed between 6-12 Amps with the bulbs we are using.

I next saw that if you look at this particular data sheet, that it has a very low resistance once it reaches its 100% heated up level (0.027 Ohms) vs. the ones above and below it on previous link have a higher final resistance (0.04 Ohms). The next category of SL15 have an even higher final resistance (0.06 Ohms). You can use Ohms Law (V=IR) to see the effect of various levels of resistance on delivered bulb voltage at these current levels.

For example once the NTC is fully heated up and has a resistance of 0.027 Ohms being used in a 5761 bulb that draws 5.5 Amps, then

V = 0.027 Ohm x 5.5 Amps
V = 0.15 Volts dropped accross that resistor once heated up -- which is pretty minor.
​

Before the NTC is heated up it has a resistance of 1 Ohm, so it looks like this:

V = 1.0 Ohm x 5.5 Amps
V = 5.5V that drops accross the "cold" NTC...blunting the spike.
​

So all I know is you need one that can take the Amp rates we are using, an initial resistance strong enough to blunt the spike, a final resistance low enough to not diminish the current delivered to the bulb.

There is a way to determine the energy rating that is discussed here, but I'm not that advanced in understanding how to use that factor in picking the correct NTC yet.

Lux,
Very well stated, I understand. BTW, your "skinny branches" are larger than most.

 

[willrx]

Is it possible to see a picture of how this NTC is attached to a light? Thanks.

 

[EvilLithiumMan]

Indeed.

The package says: "Quantity: 20", but I count 21 of them in the photo. No matter, I have ordered a few myself. Get 'em while they're hot! (I wonder if that is a thermistor joke?)

 

[rizky_p]

how do i order them? any links?

 

[EvilLithiumMan]

how do i order them? any links?

http://www.newark.com/jsp/search/productdetail.jsp?SKU=72J6730&CMP=AFC-GB100000001

I have violated a personal cardinal rule when ordering on the internet: "Always know the final purchase cost". Newark order page didn't show the shipping cost, or if they have a minimum order requirement. Newark has been around for 40 years; I'm pretty sure I won't get screwed, but won't really know until I see my Visa Card statement.

The email order confirmation I recieved states: "Shipping charge: small" - still doesn't tell me much.

 

[yellow]

Please help me. What does NTC stand for? Thanks.

negative temperature coefficient
meaning: if it gets hot, resistance lowers
(PTC = resistance ramps up according to temp. raise)

and
it is totally unimportant where the NTC sits (at postive / negative side of the batt), because - when cold - the higher resistance does not allow a sufficient initial spike to the "cold" hotwire.
Cust cut one wire and mount the resistor in.
(When aligned with the housing, it will coold down more quickly and possibly save the bulb a bit earlier. But not this important because the bulb is no longer totally cold from not being used for some time --> thats when instaflash is most common)

 

[rizky_p]

anyone willing to help buy and shipped it to me?

 

[EvilLithiumMan]

Just ordered mine today, won't have them for a few days, but I am willing to send some your way.

And even though you don't have an instaflash issue with a 633 bulb, the NTC will spare a lot of vicious arcing of the switch.

 

[LuxLuthor]

The package says: "Quantity: 20", but I count 21 of them in the photo.

Indeed. A moment of good fortune.

BTW, Yellow & others, thanks for feedback on it not mattering where you place the NTC. I seem to remember reading about "upper" and "lower" placement of p-channel FET that made me error on the side of being cautious, since I don't know as much about electronics as I would like.

 

[rizky_p]

Just ordered mine today, won't have them for a few days, but I am willing to send some your way.

And even though you don't have an instaflash issue with a 633 bulb, the NTC will spare a lot of vicious arcing of the switch.

Yes, my standar mag switch is kind of sticky sometimes even hard to press. i hopes that NTC will cures it...

 

[LuxLuthor]

There are pro's and con's to using the NTC...mainly the amp required to heat it up to 100% and have the lower specified resistance, then once it is heated up, there is a cool down time that may be 50-70 seconds (which can be facilitated with some heatsink goo against light wall).

I debated using an NTC in this 5 cell Emoli running an Osram IRC 65W bulb, but I think I'm just going to use resistors to get a 1.5V drop into the range I want, and charge a little more often.

 

[davidt]

Hey lux, I just got my NTCs today and I was testing them out before soldering to my tail spring. I am using them on my ROP HI and I noticed the NTCs got really hot quicker than I expected.

My question is if I don't heatsink the NTCs and leave them "floating" would they be damaged by heat?

Thanks