NTC soft start cures 5761 insta-flashes in MC

Northern Lights

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A new battery pack and new lot of 5761 and a light I have had no problems with were NOW insta-flashing bulbs like a 1940s news photographer! I fixed it with a soft start and reduced voltage for about $1. I put in an NTC and have at least 6.8 volts at the bulb under load. It, off course, soft starts and then has about 0.6 ohms residual resistance on the circuit but I have pleanty of voltage for it. The beam brightness is greater than my 5761s on AW soft start switch drivers on 2 AW C-cells. I put it in line with the fuse using more spade connectors. Here is the NTC
I put in:
http://www.ametherm.com/Data%20Sheets/SL12%201R010.pdf

It now resides in line with this fuse:
fusesa9.jpg


When using NTCs you must figure what the residual resitance is based on the amperage you are running against the rated amps of the NTC. It is in the data sheet. You may need to extrapolate. This part number, SL12 1R010, seems to be the best choice NTC for hot wires because it loads 1 ohm on start and has the least residual resistance at operational loads and temperature.



SL12 1R010

Max Steady State Current Up to 65°C 10.0 A

Resistance @ 100% of Max Current 0.027 oms
Resistance @ 50% of Max Current 0.060 ohms







If you use higher amperage rated NTCs that show lower resistance at 50% then extrapolate the value, say to 5.5 amps for the case of the 5761 you will find that the actual resistance is higher than this particular NTC. I obtained 7 different NTCs from Amertherm and actually tested them.


My venerable 27-year-old MagCharger with the 5761 threw me problem. I had a Sanyo AA pack, 12 AA 6P2S, 1.2Vb at 5400 mAh and it ran the 5761 fine. But I left it on a smart charger a couple of weeks and the pack went bad. Silverfox did post in 05, I think, about parallel NiMh packs getting out of balance on chargers, interesting string. Well, it happened. I appreciate the knowledge base we have here at CPF, finding that string answered my questions about the dead pack. Thanks, SilverFox!​

I built a pack on PowerX AA and they rate higher in voltage and capacity than their published nominal usually; according to a lot of RC guys. This pack should be at over 5400 mAh and the voltage at least 7.2 Vbat. I also got a new batch of 5761s. The bulbs were wider in the envelope than earlier ones I obtained and I crushed one before I realized I had to re-mod the reflector to take it. After the third charge cycle the new pack should be and is broken in, higher voltage now. After resting it one day it was still blowing, insta flashed 5761s. I do not know what the Sanyo pack Volts were under load or how much difference are in these bulbs compared to the previous ones but the result is that the PowerX 12 AA, 6S2P, 7.2 V, 5400+ mAh pack insta flashes them like flash bulbs (that is how you take a flash picture before strobe tubes were invented), there was too much Vbulb. I wish I had some original data.
Oh, well, the NTC fixed the problem even if I don't have the numbers.​

edit:
It was a comment by Yellow, last year in a thread about insta flashing that I first learned of NTCs. Great data base CPF is. Thanks, Yellow for your PMs as well that taught me about these gems.​
 
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Northern Lights

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One thing I thought of and did not say and it could be overlooked.

NTCs do not have a wide range of available ratings for low amperage and voltage flashlight applications, the residual resitance may be too much for low voltage options where only a soft start is sought.

The circuit is easily modified though, the NTCs are resitors when in a circuit so the one I found most useful if run in double or triple parallel will half or cut to one third the residual and initial resistance. So there is some adjustability. They are so cheap if you anticipate building with one, buy 4. That gives you some leeway.
 
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missionaryman

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great to hear you got them working NL - a possible far cheaper alternative for soft start regulation and a soft start C cell mag is now possible.

have you measured the voltage at the pins of the bulb yet?
 

Northern Lights

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great to hear you got them working NL - a possible far cheaper alternative for soft start regulation and a soft start C cell mag is now possible.

have you measured the voltage at the pins of the bulb yet?
Yes, in this case it is 6.6 volts at the bulb, even though the raters show the batter voltage at 7.2, some new data is beginning to show that the 5761 is best at 6.8. Above that you risk insta flash. Most people are not taking bulb voltages and would be surprise how low things really are and that the lumens they get are not what they think they have. Remember when people claimed 1000 lumens from M85s? 1000 what lumens? Most of those lights out put low 800s at best, some good ones do get up there. I intend to experiment a little with this last batch of 5761s in the light. I will put up a 2P NTC set up that should reduce the start up resistance to .5 ohms and the residual to .03. I am expection about 6.9 to the max, 7.1?ing and hopefully on a fresh pack it works, if not another insta flash, another $6. Oh, well. I hope to get back some advice first on this before I try it. I may have reached the max with this unit. It has such low circuit resitance that I may be at the limit now.
 
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Northern Lights

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great to hear you got them working NL - a possible far cheaper alternative for soft start regulation and a soft start C cell mag is now possible.

have you measured the voltage at the pins of the bulb yet?
I just split you replies in two, one for each topic. I tried higher amp rated NTCs in the C with AW cells. I had one set of cells that would click up but would insta flash 5761s, another set you could not get to run the 5761. The PCBs were obviously different. Both fired up on the NTC but that one had a higher residual resistance than SL12 1R010 and as you see from Mudman's graphs these cells sag so the Vbulb was getting pretty low quickly down into the 5-6 Vbulb range. With that model but running it with two SL12 1R010 in parallel I bet it will work. I love the AW driver/soft start but I think this mod could save the $75 cost of the driver. I will test it soon. I got that nice 2C pewter with the KIU.
I need to build a bigger shelf; so many queens. You are a great crafts man, MM, I sure could use you to help with that shelf, too bad the pond is in the way!
 

jimjones3630

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Very interesting. Don't know what your talking about expect it could do what AW driver is doing which is pretty amazing to me. And has my 3 favorits cheap, effecient, and simple.:twothumbs
 

Northern Lights

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Very interesting. Don't know what your talking about expect it could do what AW driver is doing which is pretty amazing to me. And has my 3 favorits cheap, effecient, and simple.:twothumbs
Go to this thread and look at yellows post #8:
http://candlepowerforums.com/vb/showthread.php?t=152707&highlight=ntc
look at my link above and back up to :
http://www.ametherm.com/Inrush_Current/inrush_current_limiters_pcim.htm
http://www.ametherm.com/Inrush_Current/inrush_current_faq.html
http://www.ametherm.com/Inrush_Surge_Limiters.htm
http://www.ametherm.com/Standard_SL_Data.htm
and of course it is the SL12 1R010 that had the best characteristics at operational amperage of most of the common hot wires. This could work for the likes of the 1164 too which needs a soft start.
Using three A123system cells you get 9.9 volts so with the correct NTC you can soft start and drop the voltage to 9.6 volts, cheap regulation! Here we work with a V drop , like DD an LED. V1-V2 is 0.3 volts, we want 4.22 amps so R=(V1-V2)/4.22, R=.07, here again it looks like the closest match is the SL12 1R010. The SL22 1R020 run in this application would also extrapolate to the same initial, 1 ohm and same residual at 5 amps, 0.06 ohms. But the other heat dissepation factors, max. temp etc. favor the SL12 1R010. But by looking at both data sheets you should be able to follow how I would use them. And remember by stacking these parallel you can half and third the values to suit your needs.
 

yellow

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thank You very much for mentionning my very little help
and glad You got it to work
(the time it was actual I already thought You could not find one around at Your place and to "have to" get one and send it ..) ;)
 

LuxLuthor

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Northern Lights, I sent you an email about this. It seems that the GE CL-11 12A model has a 100sec constant time (similar to Ametherm SL22 1R020) vs. your Ametherm SL12 1R010 10A that has a 47sec.

On a practical basis, how do you interpret those times?

I cannot imagine that you have to keep the light turned on for 30-40sec seconds before it reaches its low ohm parameter....and I don't see curves to see the rate drop from the 1 ohm cold at 7.2Vbulb & 5.5A in the 5761 bulb example, to 0.06 ohm hot.
 

Northern Lights

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Northern Lights, I sent you an email about this. It seems that the GE CL-11 12A model has a 100sec constant time (similar to Ametherm SL22 1R020) vs. your Ametherm SL12 1R010 10A that has a 47sec.

On a practical basis, how do you interpret those times?

I cannot imagine that you have to keep the light turned on for 30-40sec seconds before it reaches its low ohm parameter....and I don't see curves to see the rate drop from the 1 ohm cold at 7.2Vbulb & 5.5A in the 5761 bulb example, to 0.06 ohm hot.
The NTC by the manufacturer's description drops from the maximum resistance to minimum resitance in "miliseconds". The time represented in the spec you refer to is recovery time at a given temperature. That is when you shut it off after it reaches 182 degrees C it takes the NTC 47 seconds at a given surrounding temperature to cool down to reset. Reset is not an off/on condition the resistance is a gradual curve and linear so it matches to some extent the absence of the need of a soft start when the bulb filament is hot and cooling. The 47 seconds is the time determined against a given ambient temperature to cool, that is the dissipation constant. Doesn't matter in a Hot wire light because when the filament is hot you do not need soft start so the two balance out anyway. Kinda neat phenomena.

I looked up the cl-11, it has an initial resistant of .7 compared to 1 ohm, and .06 at 50% of 12 amps compared to .06 at 50% of 10 amps. It is a little lower on the initial and a little higher on the residual. This could be what you want in controling over voltage in some situations. I am planning to run 64430 on 9.9 Vbat and this could be a better solution than the SL12 1R010 because the Vbat has to be dropped to Vbulb around 9.4-9.6 we think. It is possible of course the bulb may be tough enough to run 9.9Vbulb however. That is some of the fun of the hot wire, you are in new territory and only experiments will give you diffinative answers. I guess I will insta flash and burn out a few more bulbs to answer this one accuratley.
 
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LuxLuthor

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The NTC by the manufacturer's description drops from the maximum resistance to minimum resitance in "miliseconds". The time represented in the spec you refer to is recovery time at a given temperature. That is when you shut it off after it reaches 182 degrees C it takes the NTC 47 seconds at a given surrounding temperature to cool down to reset. Reset is not an off/on condition the resistance is a gradual curve and linear so it matches to some extent the absence of the need of a soft start when the bulb filament is hot and cooling. The 47 seconds is the time determined against a given ambient temperature to cool, that is the dissipation constant. Doesn't matter in a Hot wire light because when the filament is hot you do not need soft start so the two balance out anyway. Kinda neat phenomena.

I looked up the cl-11, it has an initial resistant of .7 compared to 1 ohm, and .06 at 50% of 12 amps compared to .06 at 50% of 10 amps. It is a little lower on the initial and a little higher on the residual. This could be what you want in controling over voltage in some situations. I am planning to run 64430 on 9.9 Vbat and this could be a better solution than the SL12 1R010 because the Vbat has to be dropped to Vbulb around 9.4-9.6 we think. It is possible of course the bulb may be tough enough to run 9.9Vbulb however. That is some of the fun of the hot wire, you are in new territory and only experiments will give you diffinative answers. I guess I will insta flash and burn out a few more bulbs to answer this one accuratley.

So when you mentioned earlier in this or another thread that some other NTC's had more of a delay in reaching the low ohm reading, if they are all milliseconds going to low ohm parameter, does that that recovery "constant time" (47 vs. 100 sec) even matter for our uses?

Also, I'm just starting with the C Mags. Does anyone know the resistance of a stock setup with original spring, switch, FM bipin holder?
 

Northern Lights

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So when you mentioned earlier in this or another thread that some other NTC's had more of a delay in reaching the low ohm reading, if they are all milliseconds going to low ohm parameter, does that that recovery "constant time" (47 vs. 100 sec) even matter for our uses?

Also, I'm just starting with the C Mags. Does anyone know the resistance of a stock setup with original spring, switch, FM bipin holder?

After you asked those questions I started looking at this deeper and thought about it and have come to the conclusion because the cooling rate is quicker for the NTC than the bulb filament, or at least after the light has heated up, it does not seem to matter at all. You are absolutely correct. Therefore the other NTC that had the same resistance parameters for use with the 5761 has a slightly slower reset value. Because the NTC resistance is a function of the NTC temperature so the resitance is going up as it cools and the bulb resitance is also changing as it cools. If the bulb reaches a temperature that will cause the AW cells not to click on or for the bulb to insta flash before the NTC resets that could be a problem but It does not look like that the time differences actually matter in this case for either of the NTCs.. I think you will have enough resistance in the circuit at all times to soft start and control surge because of the combination of the filament and NTC conditions at what ever temperature ratios exist.

What could matter more than the time to cool and reset is the operating temperature at which minimum resistance is established in the NTC as this establishes time to steady state. In this case I doubt that really makes a difference as the temperatures are 182 Vs. 187 C, 5 degrees and the manufacturer states that it takes only miliseconds to reach steady state. That is not a time function that affects our applications.
Ever notice how slow the AW soft start is to reach steady state? YOu can watch that warm up it is so slow but in does not affect the practical aspects at all of the application.

I think the only thing we need to consider for NTCs in hot wires is the initial resistance and the steady state residual resistance at the current we drive these beasts at. The rest of the parameters have almost no practical application to the hot wire.

Thanks, I would never have contemplated these aspects if you had not asked.
 

JimmyM

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I was given a link to this by another CPFer looking at my PWM softstart design thread.
Neat idea. That NTC heats up to 182 deg C? That's like 360 deg F. Have you found that to be an issue in the confines of the Mag body?
I saw about the "recovery" time based on ambient temp. If the "ambient" temp in the light body gets hot from a long run, wouldn't the NTC take a while to recover? I would think that after 47+ seconds, the filament would be "cold". Would a restart cause a flash?
AWs soft start only delivers 6.8V to the bulb with a Vbat=7.2? Or has the Vbat sagged to 6.8? I've run a 5761 quite well on 7.1V and it's quite stellar.
It's hard to believe AWs soft starter drops .2-.4 volts. If that's the case, he needs to find a new mosfet. But then again I'm not sure how he's driving the gate. Vbat, charge pump, etc. It may only be getting Vbat and therefore the resistance would be a little higher when "ON". A mosfet I've spec'ed would have ~2.8 mOhms when driven with 7.2 volts. So a 7 amp load would drop 0.02 volts.
Oh well, just thinking out loud.
Nice find in the NTC though. You can't beat the price!
 

Northern Lights

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I was given a link to this by another CPFer looking at my PWM softstart design thread.
Neat idea. That NTC heats up to 182 deg C? That's like 360 deg F. Have you found that to be an issue in the confines of the Mag body?
I saw about the "recovery" time based on ambient temp. If the "ambient" temp in the light body gets hot from a long run, wouldn't the NTC take a while to recover? I would think that after 47+ seconds, the filament would be "cold". Would a restart cause a flash?
AWs soft start only delivers 6.8V to the bulb with a Vbat=7.2? Or has the Vbat sagged to 6.8? I've run a 5761 quite well on 7.1V and it's quite stellar.
It's hard to believe AWs soft starter drops .2-.4 volts. If that's the case, he needs to find a new mosfet. But then again I'm not sure how he's driving the gate. Vbat, charge pump, etc. It may only be getting Vbat and therefore the resistance would be a little higher when "ON". A mosfet I've spec'ed would have ~2.8 mOhms when driven with 7.2 volts. So a 7 amp load would drop 0.02 volts.
Oh well, just thinking out loud.
Nice find in the NTC though. You can't beat the price!

I have had no temperature problems, it must heat up to 182 at 10 amps, remember I am running it at @ 50% rating. Look over the spec sheets. The resistance is a curve. So when the NTC is cooling the filament is still hot and cooling at a rate that is seems to make no difference, a hot filament is difficult to instaflash. The NTC does not reset, it is a gradual curve up and down based on the rating in the spec. That in unison with the cooling filament seems to balance each other.
I put the NTC in the tailcap so it is not in competion to dissipate the heat in the head. I am still usning the ceramic blanket material you provided but not at the NTC.
I think there are some variances in the 5761s that come out. I have had envelope sizes change, got bigger, had ears and I broke one in a reflector that had previously accepted 5761s. I aslo had several in the last shipment start instaflashing at about 7.0-7.1 Vbulb. This NTC idea is not new but finding a compatible component was a problem because of the resitance curve in relation to the amps.
Here is another idea I am working on. I took some test readings of NTCs in parallel that led me to realize that using ohms law you can modify the resistance with parallel and series circuits like fixed resistors.
http://candlepowerforums.com/vb/showpost.php?p=2117832&postcount=133
 
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JimmyM

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NTC soft start cures 5761 instantflashes with 2xemoli, vbat 8.02, vbulb 6.8v Woo Hooo.

Thanks NL
Are those voltages steady state?
The 5761 is a 6 amp bulb right?
That's (8.02V-6.8V)*6= 7.2W power dissipation.
I belive Adam Sandle sung it best. "Nooot tooooo Shaaabyyyy"
 

jimjones3630

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vbat is with rested cells, charged 2 days ago, vbulb 6.8 steady was lower initally then rose to 6.8v
35w 6v rated.
amazing
jim

Are those voltages steady state?
The 5761 is a 6 amp bulb right?
That's (8.02V-6.8V)*6= 7.2W power dissipation.
I belive Adam Sandle sung it best. "Nooot tooooo Shaaabyyyy"
 

Northern Lights

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Jim Jones,
I read your post and I believe you are saying that the result of the build is based on the design proposal I sent? Is your success a product of our favorite NTC with no other resistor in the circuit path?
I have to re-wrap the emoli to get them into the bored light but the biggest worry is this light has a charging jack and I am so close to being out of space I may have to buy another 3C and mount the emoli without the jack if I want to keep length at a minimum.
The jack has me spoiled. Heading for bed after 12 hour night shift I simmply plug in the BC6 charger with pre-set program and voila! It is ready to go before I am, 15 minute charge time at 5Amps! No disassembly saves me and the light wear and tear.
My biggest quest for switching from AW cells to A123 and now to emoli was to get steady state bulb voltage to 6.9 volts on the 5761 without a driver. You did it first! At 6.8Vbulb.
The reason for the quest is the get the brightest 5761 light. I will ask here and skip the email to you. You and I noticed that the A123 5761 was markedly brighter than the AW cells, being the 5761 pushes them to their limits and the A123 had the flatest discharge curve I have seen. Makes the light look regulated. Can your last success answer this question:
IS THE 5761 ON EMOLI NOTICEBLY BRIGHTER THAN THE A123 VERSION?
If it is brighter I will use it for my personal light. I want maximum torch-lumens and throw. I must figure a way around that charging Jack problem, I think adding the AW spacer will solve the problem but that is adding another 10mm to a 3C cell light, and that is already 1 cell longer than I like for the purpose I began building a light in this project. That will be an annoying extra 70mm. Going to a 4c size would make it 100mm longer than I wanted.
Well, I will keep buiding and experimenting untill I am satisfied with the "Perfect 5761". I have too many lights now, good lights that I will never use. Tomorrow I will boot two lights over to b/s/t, a 5761 2C on AW cells with jack and driver and an 1185 3C, AW cells with jack and driver to make room for more mod building.
That will demonstrate to Mrs. Northern Lights that I AM a reasonable person, after all.
 

jimjones3630

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Yes based on your proposal, our favorite NTC without any other resistor in circuit path!!
The convenience of jack charing is a big plus and will have to address that at some point.

Every since sun set I've been outside, my neighbors going to think I'm crazy as a loon.

Took 1164 with 8 fresh charge eneloops, 64610 on 3xA123 10.2vbat. swapped out 64610 since looked kind of sick and put in tungsram 56580,
tungsram 56580 on 3 A123 9.78vbat, 5761 with said 2xEmolis.

At one point Emoli power 5761 was looking brighter than 64610, bat check reveiled way. Only think can say is 5761 with 2 emoli is not brighter than 64610 or 56580.

What need is side by side A123x2 and 2xEmoli with NTC because they are close.


Jim Jones,
I read your post and I believe you are saying that the result of the build is based on the design proposal I sent? Is your success a product of our favorite NTC with no other resistor in the circuit path?
I have to re-wrap the emoli to get them into the bored light but the biggest worry is this light has a charging jack and I am so close to being out of space I may have to buy another 3C and mount the emoli without the jack if I want to keep length at a minimum.
The jack has me spoiled. Heading for bed after 12 hour night shift I simmply plug in the BC6 charger with pre-set program and voila! It is ready to go before I am, 15 minute charge time at 5Amps! No disassembly saves me and the light wear and tear.
My biggest quest for switching from AW cells to A123 and now to emoli was to get steady state bulb voltage to 6.9 volts on the 5761 without a driver. You did it first! At 6.8Vbulb.
The reason for the quest is the get the brightest 5761 light. I will ask here and skip the email to you. You and I noticed that the A123 5761 was markedly brighter than the AW cells, being the 5761 pushes them to their limits and the A123 had the flatest discharge curve I have seen. Makes the light look regulated. Can your last success answer this question:
IS THE 5761 ON EMOLI NOTICEBLY BRIGHTER THAN THE A123 VERSION?
If it is brighter I will use it for my personal light. I want maximum torch-lumens and throw. I must figure a way around that charging Jack problem, I think adding the AW spacer will solve the problem but that is adding another 10mm to a 3C cell light, and that is already 1 cell longer than I like for the purpose I began building a light in this project. That will be an annoying extra 70mm. Going to a 4c size would make it 100mm longer than I wanted.
Well, I will keep buiding and experimenting untill I am satisfied with the "Perfect 5761". I have too many lights now, good lights that I will never use. Tomorrow I will boot two lights over to b/s/t, a 5761 2C on AW cells with jack and driver and an 1185 3C, AW cells with jack and driver to make room for more mod building.
That will demonstrate to Mrs. Northern Lights that I AM a reasonable person, after all.
 
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