Auto ramp to full after thermal protection ramps down

smegoal

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Dec 25, 2018
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Hi I am looking for a driver which will ramp output down when it's too hot but will ramp back up when it cools down. So I can set it to max and ride slowly up the hill (with some complete stops as well), it will gets hot and ramp down then as I start to descend it will automatically ramps back up as the air moving past it cools it down. One of the commercial bike light I have does this and it is very handy especially on undulating terrain so I don't have to keep remembering to turn it back to full at the top of every hill. I am planning on building a helmet mounted light with a remote battery bank in a backpack (to keep the weight on the helmet down or it moves around too much).

So far I have a lot of different ideas but if any of you can recommend a driver which can do this type of thermal management I will be picking parts to suit the driver. If possible I would like to stay at higher voltages especially with the remote mounted battery.

I am quite new to this hobby (torches not the mountain biking) so far I have ordered a S2+ with a triple so I can play around with some different brightnesses and optics to work out how much power I really need and how wide a spot is suitable (And cos it's going to be lit).

PARTS for the triple:
Carclo Lens – 3-UP Frosted Medium Spot
FET + 7135 Driver – 17mm – MTN-17DDm with spring bypass
Copper Triple Spacer for Convoy S2
Nichia NVSW319AT D440 5000K 70+ CRI LEDs on 20mm 3XP Copper Noctigon + Pre-Bridged
Sony 18650 VTC5A

I was a bit concerned that the switch may not handle the current but after much forum scrolling I could not find evidence of instant catastrophic failure. If you can see anything glaringly obvious wrong with my triple please do point it out as you may save me from having to replace parts.

Currently I have a DUO and a single mountain bike light. They are pretty good the duo auto ramps while the single stays on full all the time. However the single is a bit narrow so when you are cornering there is a dark gap between the bar mounted duo and the helmet mounted single. Also the single could do with being a bit brighter.
 
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archimedes

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Hello and welcome to CPF

Your post above has been approved, in lightly edited form (since all bold font and no paragraph breaks is difficult to read)
 

smegoal

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Dec 25, 2018
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Thanks you. I gave into the temptation to post without previewing after copy and pasting from my post on budget light forums.
 

DrafterDan

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Jul 28, 2013
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Phoenix, AZ
I do a good deal of bicycle riding (completed my first century this year).

I just use a Cygolite 250 on my road bike. Even on my cyclocross for trail rides, I rarely need full power.

The Convoy S2 is a good host, but if you run 100% as long as possible, a simple ramp down might not be enough to allow efficient cooling. The S2 is a pretty small torch, and doesn't have a lot of mass. My triple build works quite well with the stock switch, so at least there's that.

0YKMbN.jpg
 

smegoal

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Dec 25, 2018
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The s2+ is just to test brightness and angle to find a minimum which provides enough light. I had toyed with the idea of using a s2+ with remote batteries but since then I have found a more suitable host 36mm housing
We ride a mix of xc and downhill so the more light the better.
Thanks you for the feedback on the switch.

 

alpg88

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Apr 19, 2005
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5,282
i can't think of any ready made driver with ramp up\down, like you want, that will fit into s2+

i ride with s2+ xml2 for about 2 years, 8 amc driver. run it on high on the go. no thermal control at all. it does get hot, but not too hot, so far i can not notice any degradation by eye. when it dims, i'll replace the led, it is not hard nor expensive. rather do that once in few years, than get expensive exotic drivers\lights.
 

staticx57

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Dec 2, 2011
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NJ
The driver you selected when paired with Bistro firmware has thermal regulation
 

DIWdiver

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Jan 27, 2010
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Connecticut, USA
I just checked the Bistro firmware code, and it does automatically ramp back up after it cools down.

I've been curious what a FET+7135 driver is, so I looked it up. It looks like you have the option of running either FET (direct drive, no regulation) or 7135 (350 or 380 mA regulated) output. Various firmwares will use these options differently. The brief descriptions do not mention which mode(s) they use. I'd guess many use FET mode exclusively, but that's only a guess.

In FET mode it will be somewhat difficult to quantify the output, as you will have to somehow measure the actual current, which will change significantly with battery voltage, wire resistance, meter resistance, and even LED temperature. For best results, you would need to measure the current during your tests of light output. It might be easier to get a multiple-7135 driver and make tests at known fixed currents. You can add/remove 7135s to change the output current.
 
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smegoal

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Dec 25, 2018
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That's great thanks. Only the test S2+ will run the fet because I want a stupidly bright torch just to see how bright bright really is. The plan is to find a 7135 driver with auto ramp up (so any driver with bistro). Then estimate how bright and wide I need it based off some testing with the s2+, then add or remove 7135s till output matches my needs. For testing I can measure the amps and adjust voltage or resistance to try different current levels.

As far as I could understand most of the fet/7135 drivers allows you to use the 7135s as moonlight and low light levels then the FET for the higher and turbo levels (If anyone whos had a play with one of these want to correct me please jump on in).
 

smegoal

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Dec 25, 2018
Messages
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I understand that it ramps down when it exceeds a set temp i just wanted to know if It ramped back up or do I need to press the button. Some one has answered that for me below.
Thanks you for your reply.
 
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