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Thread: Adjustable 10A linear LED driver - New and Improved!

  1. #181
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    Default Re: Adjustable 10A linear constant current driver

    Quote Originally Posted by bigterk View Post
    sent funds via paypal today for 2 drivers as follows:IS1006-0512 5 1.2
    IS1006-1025 10 2.5
    Got it. I can ship those on Monday.

    Thanks!

  2. #182

    Default Re: Adjustable 10A linear constant current driver

    PayPal sent for Two IS1006-1025!

  3. #183
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    Default Re: Adjustable 10A linear constant current driver

    Got your payment. I have those in stock, so will ship tomorrow. Thanks!

  4. #184

    Default Re: Adjustable 10A linear constant current driver

    General question about the schematic.

    Some of the resistor values don't seem to be labeled. I guess the 6 on the end is confusing. For example, is R3 a 36K or a 3K ohm resistor?
    R1 R3 R2 R8
    0R05 3K6 3M6 3K6

    Also, R8 shows no connection. From where R8 is placed on the schematic it looks like maybe it is connected between the (-) terminal on the op amp and in between the source of the FET and R1 but I'm not sure.

    General question about the operation. (just curious how it works)

    It looks like the switch connections H, L, & C setup a a voltage divider which determines the amount of voltage applied to the (+) terminal on the op amp. The H-C connection gives a higher input voltage than the L-C connection. I'm not sure what the specific configuration of the op amp is and how to relate input to output voltage but I'm assuming it's not setup to rail one way or the other (like a comparator) but rather the higher input voltage the higher output voltage? This would in turn determine the amount of voltage applied to the gate of the FET and change the amount of drain to source current. I've seen similar type circuits before and have always been confused as to how they work. I'm not sure if the resistance of the FET is changing signifigantly enough to vary the current or if something else is happening.

    Regardless of my limited understanding... cool design and I'm getting excited about setting up my SBT-90 build with one of these drivers.

  5. #185
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    Default Re: Adjustable 10A linear constant current driver

    You seem to understand fairly well so far.

    Since decimal points are easy to loose or miss, we often use the convention of replacing it with a multiplier, thus 3.6K becomes 3K6, and 0.005 ohms becomes 0R005, or R005.

    One way to think of a FET is as a voltage-controlled resistor. When the FET is 'on' the resistance is very low. This resistance is one of the primary specs of the FET. When it's 'off' the resistance is very high. Many applications use the FET in only 'on' and 'off' conditions. But there is a region between on and off where the resistance changes with gate voltage. This circuit uses the FET in that region. And yes, the resistance changes a lot (many orders of magnitude).

    The op-amp and FET are set up as a constant current sink. The current flow through R1 is the same as that through the FET, and more importantly, the same as the LED. The voltage developed across R1 is compared to the reference voltage from the divider circuit. If it's lower, the op-amp increases the voltage on the gate of the FET, thus causing it to conduct more current. If the voltage is higher than the reference, the op-amp reduces the gate voltage, thus reducing the current. Since the gain of the op-amp is very high, only a tiny change in sense voltage (across R1) is needed to cause a large change in gate voltage on the FET. Thus the sense voltage is always kept very close to the reference voltage, which means the LED current is kept constant, no matter what the conditions. It only changes when the reference voltage changes. Variations in input voltage, temperature, and between individual parts cause the gate voltage requirements to change, but the LED current is practically independent of these fluctuations. It depends only on the value of R1 and the reference voltage. These can be kept pretty constant.

    If you're wondering what R2 is for, it provides a little negative offset. The op-amp has a small and unpredictable offset between the two inputs. If I didn't correct for this, it's possible that there would still be some current in the LED even when the reference voltage is taken to zero (which should turn the LED off). R2 overcomes the offset in the op-amp and guarantees that the output will be zero when the reference voltage is zero.

    C1 and R8 reduce the bandwidth of the circuit, to prevent it from oscillating.

  6. #186

    Default Re: Adjustable 10A linear constant current driver

    Pretty cool. Thanks for the detailed explanation! I understand now how the constant current portion works. That works out nice how the op amp takes care of where the FET is operating and all you have to worry about is the reference voltage, size of R1 and what you want the current to be.

  7. #187

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    DIW,
    I'd like 2xis1006-512. $54.95. Is that correct? Thanks.

    -1115

  8. #188

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    HI
    a quick question, can your driver work with positive grounding leds, such as luminous pt54,etc?
    thanks

  9. #189
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Quote Originally Posted by jwhughes1115 View Post
    DIW,
    I'd like 2xis1006-512. $54.95. Is that correct? Thanks.

    -1115
    Actually, shipping is now $5.15, so the total is $55.15.

    Sorry for the delay, I had somehow missed that there was an update in the thread.

  10. #190
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Quote Originally Posted by MUSTARD View Post
    HI
    a quick question, can your driver work with positive grounding leds, such as luminous pt54,etc?
    thanks
    What's a pt54? I did a search at Luminus.com and came up with two obscure references that didn't tell me anything useful.

    I would guess that 'positive grounding' means that the + terminal of the LED is connected to the metal substrate of the module. Is that correct?

    In any event the answer is yes, it will work, if you properly isolate the necessary parts. The driver works with the + terminal of the LED connected to the + terminal of the battery (B+ and L+ are connected at the driver), but the - terminal of the LED which connects to L- on the driver, must not be connected to anything else. The thermal tab of the driver is connected to this terminal as well, so in most cases you have to electrically isolate the thermal tab from the heatsink. This only becomes unnecessary if the heatsink is not connected to anything else in the circuit (which is pretty unusual in flashlights).

  11. #191

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    I have to bother you with another question.
    using a sst 90 RED emmitter which is fv-2.2v and 6.3 amp plus, will your driver work with this given appropriate batteries that are close to emmitter specs?
    thanks

  12. #192
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Yes, it will work. The only question is how much of a heat problem will you have. The driver has a minimum input voltage of 3.2V, so you can't go really close to the emitter voltage. But a single Li-ion cell should work, or 3 NiMH in series, and the heat problems would be managable.

  13. #193

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    CAN YOU GET THE INPUT VOLTAGE DOWN ON THE DRIVER WHEN BUILKDING IT?

  14. #194
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Quote Originally Posted by MUSTARD View Post
    CAN YOU GET THE INPUT VOLTAGE DOWN ON THE DRIVER WHEN BUILKDING IT?

    I could get the input voltage as low as 2.7V with only a minimal re-design (new parts, not new boards). That would be a $10 customization fee since you are looking at more than a current setting change (which would be $5).

    Keep in mind that the driver has a 0.25-0.30V dropout voltage (input voltage must be 0.25-0.30V higher than output voltage to achieve full power). This could be reduced to around 0.15V in a full custom design at slightly higher cost.

  15. #195

    Default Re: Adjustable 10A linear constant current driver

    Hello DIW,
    to keep the thread alive, here is what i want : 2

    IS1006-1025 10 2.5

    is there datasheeto to come with it?

  16. #196
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    Default Re: Adjustable 10A linear constant current driver

    There's a data sheet, but I don't include a hard copy. I can e-mail it to you now if you like. Just post or PM me your e-mail address.

  17. #197
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    Default Re: Adjustable 10A linear constant current driver

    Am I correct in assuming that these would work well for driving a SST-90 via automotive application? I'm looking to utilize this as a driver for some driving lights on my motorcycle. Obviously I would need the input voltage capable of handling more than 12V. I love the dual output with switch option as I can choose to go high/low for in town and on highway.
    If it can't be modified, I don't want it.

    DX 30mw 50mw. BFG (phraug) 150mw putting out 120mw Homemade 100mw, 150mw DVD burner laser.

  18. #198
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    Default Re: Adjustable 10A linear constant current driver

    Several people in the automotive forum are using it already, or at least building with it. I replaced a few parts and added some external protection components for them.

    There seemed to be enough interest that I actually designed a special board just for automotive use. I'll be building the first prototype tomorrow. It will have better protection from the nasty automotive electrical environment, better power-handling, and some thermal protection as well. If all goes well it will be available for sale in the next few weeks. Of course it could be much longer than that if something DOESN"T go smoothly.

    You may also want to check out the automotive forum for discussions of legal issues around making your own vehicle lights. The guys I've sold to are all planning on using them off-road only.

    Either the IS1006 or the IS1011 would be suitable, but they will both have serious thermal issues unless you run three LEDs in series. It's been discussed ad nauseum previously, read back if you're interested in the details. There are other drivers that might be better for a single LED.

  19. #199
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    Default Re: Adjustable 10A linear constant current driver

    Quote Originally Posted by DIWdiver View Post
    Several people in the automotive forum are using it already, or at least building with it. I replaced a few parts and added some external protection components for them.

    You may also want to check out the automotive forum for discussions of legal issues around making your own vehicle lights. The guys I've sold to are all planning on using them off-road only.

    Either the IS1006 or the IS1011 would be suitable, but they will both have serious thermal issues unless you run three LEDs in series. It's been discussed ad nauseum previously, read back if you're interested in the details. There are other drivers that might be better for a single LED.
    I'm not concerned about legal issues. They will essentially be "fog lights" and there is nothing illegal about using them on the roads as long as they are not in folks's eyes.

    I'm not concerned about thermal protection either as the driver will be mounted on the opposite side of this heatsink:
    http://www.mouser.com/Search/Product...88-SV-LED-176E

    Was looking at using either the ​IS1006-0820 or the IS1006-1025
    If it can't be modified, I don't want it.

    DX 30mw 50mw. BFG (phraug) 150mw putting out 120mw Homemade 100mw, 150mw DVD burner laser.

  20. #200
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    Default Re: Adjustable 10A linear constant current driver

    That heatsink should be suitable, as long as the airflow over it never drops below 10 mph. In still air, it would rise to around 275 C, which wouldn't be good at all.

    Unfortunately, the heatsink isn't the only problem. If you run one LED on an IS1006-0820, the driver will dissipate about 80W. Short of soldering the FET directly to the heatsink (which would then require that you electrically isolate the heatsink), there's no way to get that much heat out of the FET and into the heatsink without unacceptable temperature rise. The practical limit is around 30W, which is about what you get running three LEDs in series.

    If building fog lamps, I strongly suggest you read this first.

  21. #201
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    Default Re: Adjustable 10A linear constant current driver

    Quote Originally Posted by DIWdiver View Post

    Unfortunately, the heatsink isn't the only problem. If you run one LED on an IS1006-0820, the driver will dissipate about 80W. Short of soldering the FET directly to the heatsink (which would then require that you electrically isolate the heatsink), there's no way to get that much heat out of the FET and into the heatsink without unacceptable temperature rise. The practical limit is around 30W, which is about what you get running three LEDs in series.
    As long as the bike is on, it will be moving faster than 10mph. I can honestly say that I've never ridden the bike slower than 15mph. Unfortunately, the bike has a LOT of torque and I cannot take off without it instantly speeding past 10mph in the first second or two. The Yamaha V-max is known for it's power.

    Your concern is however noted. I can't imagine using more than 2 Lights on this bike though.. just seems like overkill. Any way to add additional lower powered LED's into the mix? Say like 2 XM-L's?

    How about a Peltier affixed to a heatsink with the driver on the opposite side? I have a Peltier pulled from a C@sio Projector that had a SST-50 red led mounted onto it. I used the projector to harvest for blue Laser diodes.

    Sorry, not meaning to clutter up your sales thread with discussions on lights and such.
    If it can't be modified, I don't want it.

    DX 30mw 50mw. BFG (phraug) 150mw putting out 120mw Homemade 100mw, 150mw DVD burner laser.

  22. #202
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    Default Re: Adjustable 10A linear constant current driver

    No problem cluttering up the thread, it's pretty bad already. Plus I always intended it to be for discussions like this.

    As long as you keep the bike moving, the heatsink isn't the problem, it's the FET thermal interface, so the Peltier isn't going to help. Also, one intended for use with an SST-50 probably wouldn't handle the heat flux we're talking about.

    You could add 3 XM-Ls, parallel to each other but series with the -90. Then you would have 2.67A in each XM-L and 8 in the -90, and less heat in the driver. If you added a 1-ohm 10W resistor in series with each XM-L, then they would current share very well and you'd releive more stress on the driver. In fact I'd be tempted to put two in series with each XM-L. That would reduce the max power in the driver to around 15W, which is very managable. It would mean that you'd need a tad over 12V to get full power in the LEDs, but I'd guess that wouldn't be a problem for you.

  23. #203

    Default Re: Adjustable 10A linear constant current driver

    Quote Originally Posted by Kenom View Post
    I'm not concerned about legal issues.
    You need to be concerned about legal issues, which are a good bit more important and specific (and applicable) than you seem to realize. Laws and regulations do not cease to exist simply because you aren't aware of them, don't understand them, or don't like them. Homemade lamps are not legal, unless you build them, have them tested, and certify them in accordane with the applicable technical regulations. That is a prohibitively difficult and costly proposition for a one-off kind of deal. You don't get to just declare the lights you build as fog lamps (or whatever) and call it good. The lighting modifications/products you're asking about or recommending are illegal. Rule 11 of this board prohibits advocating illegal activity. Stop it now, please.

  24. #204
    Flashaholic Kenom's Avatar
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    Default Re: Adjustable 10A linear constant current driver

    Quote Originally Posted by Scheinwerfermann View Post
    You need to be concerned about legal issues, which are a good bit more important and specific (and applicable) than you seem to realize. Laws and regulations do not cease to exist simply because you aren't aware of them, don't understand them, or don't like them. Homemade lamps are not legal, unless you build them, have them tested, and certify them in accordane with the applicable technical regulations. That is a prohibitively difficult and costly proposition for a one-off kind of deal. You don't get to just declare the lights you build as fog lamps (or whatever) and call it good. The lighting modifications/products you're asking about or recommending are illegal. Rule 11 of this board prohibits advocating illegal activity. Stop it now, please.
    What makes you think I am not going to take the prohibitively difficult and costly proposition or that this is a one of a Kind deal? When I tackle a project of this size, it's not for just my own person use. It's also for a manufacturing standpoint. It's all part of the research and development of a product. He was discussing legal issues which are not relevant to the discussion of the driver, hence my comment that I wasn't concerned about the legal issue. I appreciate you looking out for the board, but nothing discussed is illegal.
    If it can't be modified, I don't want it.

    DX 30mw 50mw. BFG (phraug) 150mw putting out 120mw Homemade 100mw, 150mw DVD burner laser.

  25. #205

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Quote Originally Posted by DIWdiver View Post
    Actually, shipping is now $5.15, so the total is $55.15.

    Sorry for the delay, I had somehow missed that there was an update in the thread.

    No worries. I think part of the delay was actually mod time because I don't have my three posts in yet. Of course I was out of country when you replied. Sorry for the long delay. PP incoming.

  26. #206

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    can you make a 10 amp or 8 amp driver with a low setting of 5 or 6 amp??

  27. #207
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Yes, that's just a matter of changing one resistor.

  28. #208

    Default Re: Adjustable 10A linear LED driver - New and Improved!

    Hi, What is the minimum driver input voltage differential OVER the led's forward voltage in order to be in regulation before going in DD mode. I wish to use a 7.2 VDC as input but the led's Fv is 6.2V. Would that bee too close ?( 1V over)
    Also if I use an potentiometer for dimming, will that dimming be PWM or not ? and finally, if I throttle down the current to about 5 A to the leds via the potentiometer, will that cause excess heat due to power that has to be "burned"?.

  29. #209
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    Default Re: Adjustable 10A linear LED driver - New and Improved!

    How much for shipping to North Carolina?

  30. #210

    Default Re: Adjustable 10A linear LED driver - New and Improved!


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