NTC Thermistor (SL12 1R010 ) working well ( Update)

[Anglepoise]

I just recently received my order of NTC thermistors and I am here to report that I can now take a fully charged set of AA batteries, hot off the charger, and use them immediately to power up my 5761 without any more flashing.

 

[smopoim86]

Re: NTC Thermistor (SL12 1R010 ) working well

congrats. I blew mine the other day. I may have to try that. Although, I bought a 5 pack of bulbs from KD that seems to be almost as bright and work just fine.

 

[Northern Lights]

Re: NTC Thermistor (SL12 1R010 ) working well

Great, when I first found that NTC it worked so well, at 5 amps, exactly 50% the max amps, those were working at 0.06 ohms as specified.
Since then I have not got a batch that has worked correctly, some of the readings put them at high as 300% over the expected resistance.
I am glad it is working for you. One test I have done is hooking up the DMM parallel at the bulb to get bulb voltage when running. That will tell you if the NTC is too high a resitance or just right.
Ametherm has been working with me on this. I just got some recommedations last week from the chief engineer for our usages of the 5761 bulbs.
So far, I have not got it working just the way I want yet. They implied they may make a special batch.

 

[Anglepoise]

Re: NTC Thermistor (SL12 1R010 ) working well

Great, when I first found that NTC it worked so well, at 5 amps, exactly 50% the max amps, those were working at 0.06 ohms as specified.
Since then I have not got a batch that has worked correctly, some of the readings put them at high as 300% over the expected resistance.
I am glad it is working for you. One test I have done is hooking up the DMM parallel at the bulb to get bulb voltage when running. That will tell you if the NTC is too high a resitance or just right.
Ametherm has been working with me on this. I just got some recommedations last week from the chief engineer for our usages of the 5761 bulbs.
So far, I have not got it working just the way I want yet. They implied they may make a special batch.

I have not tested the ones I recieved. I was just so happy that I could slide in my fully charged 'six pack" and not have the 5761 bulb flash. I am not quite sure the best way to test but would like to know just how much additional resistance is being fed into the circuit when warm.

 

[Northern Lights]

Re: NTC Thermistor (SL12 1R010 ) working well

I have not tested the ones I recieved. I was just so happy that I could slide in my fully charged 'six pack" and not have the 5761 bulb flash. I am not quite sure the best way to test but would like to know just how much additional resistance is being fed into the circuit when warm.

nearly impossible to measure directly the NTC hot resistance, quite easy to get the R @ 25*C though.

To figure the resistance of the circuit, which for the most part is the NTC do this.

When opperating take the voltage of the running cell, that is Vbat.
Then take a parallel connection at the bulb with a DMM, that is the bulb voltage, Vbulb
Use the meter to get the amps of the in use circuit, the meter goes in series, I hook either to the bulb or at the batter ground, tail cap. Amps is I.

The difference between Vbulb and Vbat is Delta V or the Voltage drop.

Use Ohms law.

dV/I = Rntc , the voltage drop divided by the amps will tell you how much resitance is in the circuit which in your case is almost all NTC.

an example
7.5 volts at the Emolis under the load of the bulb
7.3 volts at the 5761
pulling 4.5 amps

0.2 / 4.5 = 0.04 ohms, the NTC of course is dropping from the high resistance to this at steady state, 0.04 ohms @ I max of 4.5 amps.

his is an ideal situation for an emolie powered 5761. I built one with the same NTC you are using and a parallel resistor. It was the brightest 5761 I ever made. I think its current owner has it in B/S/T right now.

 

[Anglepoise]

Re: NTC Thermistor (SL12 1R010 ) working well

Thanks NL for your info on testing using ohms law. Will set up a test in the next few days and report back. Absolutely no point in using these NTC's if they reduce the bulb brightness so much that one would be better off using a lower powered bulb ( WA1111) and no NTC.

 

[SafetyBob]

Re: NTC Thermistor (SL12 1R010 ) working well

Northern Lights, I have to ask......exactly where and why did you add the resistor to your light?

Am I correct that you were fine tuning amperage to the bulb to prevent to much power going to the bulb after the NTC did it's thing?

Bob E.

 

[Northern Lights]

Re: NTC Thermistor (SL12 1R010 ) working well

Northern Lights, I have to ask......exactly where and why did you add the resistor to your light?

Am I correct that you were fine tuning amperage to the bulb to prevent to much power going to the bulb after the NTC did it's thing?

Bob E.

My first experience:
NTC soft start cures 5761 insta-flashes in MC
I have put some up near the socket or in the slots on the side of the switch but the tail cap has been best for me.

Amps to the bulb is no problem, it is voltage spikes. Inrush current limiters specs are based on Amps but correspondily they reduce voltage. So my references to amperage is all about finding the NTC that will have the least resistance at steady state. Some companies publish less than steady state resitance values. NTC specs are based on a maximum Amp rating for the NTC.

If steady state resistance is too high, your voltage drop off the pack a little to much but not too far off by adding parallel resistors you can by ohms law lower the total resistance and still have inrush current protection. Study the www.ametherm.com site for a lot of technical stuff on this.

NTC and fuse in the tail cap, plexiglass isolates the ground:

NTC in the tower area, modified with parallel resistors; a charging jack is present on the switch.

 

[SafetyBob]

Re: NTC Thermistor (SL12 1R010 ) working well

OK, got it. The pictures are excellent, truly explains it all.

Since that is a red fuse, 10A right?

Bob E.

 

[lctorana]

Re: NTC Thermistor (SL12 1R010 ) working well

Hmmm, fuse.

Yes, fuse.

Adding a fuse is something I must start doing, and soon, now I'm into serious hotwires...

 

[Lightfantastic]

Re: NTC Thermistor (SL12 1R010 ) working well

Where can one procure these devices in small quantities?

 

[Northern Lights]

Re: NTC Thermistor (SL12 1R010 ) working well

Where can one procure these devices in small quantities?

Jim Jones has a thread, he accidently double some orders.
FS Emoli $16, A123 $14, some bulbs, NTCs, windows, chargers.

 

[Northern Lights]

Re: NTC Thermistor (SL12 1R010 ) working well

OK, got it. The pictures are excellent, truly explains it all.

Since that is a red fuse, 10A right?

Bob E.

A Fuse Saved My Hot Wire! (PICTURE!) link

 

[SafetyBob]

Re: NTC Thermistor (SL12 1R010 ) working well

Northern Lights, thanks, great picture and good story for me before I build my first really powerful hotwire, I need to ensure I have safety built in!!

Bob E.

 

[Anglepoise]

UPDATE. Well the NTC Thermistors are still working well ( no flashed bulbs ) but I feel that the voltage drop is just too great to make this a 'fix' for my combination. Without NTC, i was able to get the following results. 7.76 resting battery voltage. 5.06 Current draw on the 5761 bulb. And 7.31 volts with bulb illuminated. That works out to 90 milli ohms of resistance if my math is correct. Now when I introduce an NTC in to the circuit, the measured voltage drop increased to 7.15 , which on the surface looks quite reasonable , but the light reduction was very noticeable. My solution has been to make up two identical tailcaps, one with NTC, one without so I can full charge and use the light right away without worry. Not the best solution but........

 

[lctorana]

My experience with the RS Components NTCs is that the NTC resistance (& voltage drop) continues to decrease for a few MINUTES after switchon.

And the lower the current draw, the longer this takes.

In my Roar of the Dolphin (2A) this seems to take forever. Some of my really angry hotwires reach steady state much quicker, but even those don't reach 99% for nearly two minutes.

But I don't mind that.