SparkFun Electronics Commentsurn:uuid:214d0e4e-f1b1-d287-ce26-ac5b4c9f82492024-03-28T07:17:55-06:00SparkFun Electronicssantaimpersonator on COM-13716 - FemtoBuck LED Driversantaimpersonatorurn:uuid:4e9069c5-e939-d198-8b25-f08e5802a78c2020-08-01T02:11:34-06:00<p>Hi there, it sounds like you are looking for <a href="https://www.sparkfun.com/technical_assistance" rel="nofollow">technical assistance</a>. Please use the link in the banner above, to get started with posting a topic in our <a href="https://forum.sparkfun.com/" rel="nofollow">forums</a>. Our technical support team will do their best to assist you.<p>Unfortunately, your question appears to be outside the design scope for this product. Therefore, you may need to refer to the <a href="https://cdn.sparkfun.com/datasheets/Components/LED/AL8805.pdf" rel="nofollow">datasheet</a> and <a href="https://cdn.sparkfun.com/datasheets/Components/LED/femtobuck_v12.pdf" rel="nofollow">schematic</a> to figure that out on your own.</p></p>
grasping_dude on COM-13716 - FemtoBuck LED Drivergrasping_dudeurn:uuid:7becb980-562a-be23-40ff-aad933eb94c02020-07-27T15:46:18-06:00<p>Will this work as a current controller for changing speed of a 2V micro motor?</p>
JetForMe on COM-13716 - FemtoBuck LED DriverJetForMeurn:uuid:e99fba51-28a2-d2bb-4ae9-39997877c71c2020-04-01T22:42:50-06:00<p>I can't quite tell from the data sheet, but if I use PWM at the CTRL pin, will it cycle the driven LED at the PWM rate, or will it stay on during the PWM off cycle and just adjust the current drive accordingly?<p>I'm trying to avoid flicker in the driven LED.</p></p>
santaimpersonator on COM-13716 - FemtoBuck LED Driversantaimpersonatorurn:uuid:496915dd-8c2d-e42e-be0d-e75a528747792019-05-10T12:00:08-06:00<p>For technical assistance, please use the link above to post a new topic on our forum page.</p>
JAVASka on COM-13716 - FemtoBuck LED DriverJAVASkaurn:uuid:ff805934-5146-44a9-bcb5-2a9677e74c5f2019-05-09T08:42:08-06:00<p>Hello!
I am building a dimmable LED Light for a Raspberry Pi camera.
Is this appropriate for that purpouse or will I get band effect?
Thanks!</p>
Customer #450785 on COM-13716 - FemtoBuck LED DriverCustomer #450785urn:uuid:24b249d3-1fbc-8a9f-9af9-25cf1d1a6d1a2018-10-26T18:23:39-06:00<p>I haven’t gotten one of these drivers <em>yet</em>, but if the description is accurate you can fully control it with a RasPi with a single GPIO.</p>
Customer #1450418 on COM-13716 - FemtoBuck LED DriverCustomer #1450418urn:uuid:728f7049-3b69-eba5-51e1-7108c52d1ec12018-10-10T09:37:51-06:00<p>Does the LED driver work with Raspberry Pi?</p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:43c73e9a-52c0-393a-6f9e-cc421cb8a7582018-03-29T09:26:47-06:00<p>No. You'd blow out both of the FemtoBucks.</p>
Madaeon on COM-13716 - FemtoBuck LED DriverMadaeonurn:uuid:f13054fe-7dff-51af-4bd3-33946c640a832018-03-29T02:36:16-06:00<p>If I have a power supply of 42V, can I connect in series two femtobucks,
where each one is driving some Leds in series for a total of 21V, 670mA?</p>
Customer #505910 on COM-13716 - FemtoBuck LED DriverCustomer #505910urn:uuid:9f5e6806-27a1-7ba4-d824-2bdaae40e9772017-04-04T11:34:19-06:00<p>Thanks! I'll get a couple ordered.</p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:5129a068-50e1-59a3-672d-ebdf14d4facf2017-04-04T09:23:40-06:00<p>A quick test shows that it operates fine at 6.0V. It cuts out around 5.8V, so you should be fine at 6.4.</p>
Customer #505910 on COM-13716 - FemtoBuck LED DriverCustomer #505910urn:uuid:5e19d877-1458-9d94-3375-e3b48f0f9dff2017-04-04T08:53:53-06:00<p>Can anyone verify the minimum operating voltage? I want to drive one, 3 watt LED using a 2-cell LiFePO4 battery (6.4 volts nominal, 7.3 at full charge). The data sheet says 6 volt minimum, but the tutorial video says 7. If 6v is right, I should be fine.<p>Which is correct?</p><p>Thanks,</p><p>Randy</p></p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:f37b4b9d-2e42-ee54-7750-e286accb18912016-06-27T09:32:17-06:00<p>I doubt it. Modulating the control pin is going to cause the driver to reduce its current output, but I don't believe it actually modulates the output, just changes the feedback set point.</p>
paolofi on COM-13716 - FemtoBuck LED Driverpaolofiurn:uuid:dde43482-f982-44c2-4a60-c77c0c2e9e5c2016-06-24T18:40:11-06:00<p>The control pin can be used to modulate some led at 38Khz for IR use?
Thanks.</p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:9f421ef2-0628-d368-b853-a42f0c26bcf22016-02-04T12:56:35-07:00<p>You can do this, but it's not recommended. You'll need one low resistance (1-2 ohm) high power (1-2W) resistor per leg, to provide a resistive element allowing the strands to have different LED forward voltages.<p>It's best if the LEDs on all branches are the same; the more different the forward voltages of the strings of LEDs are, the worse the balancing is.</p><p>When you do this, the drive current will be more or less evenly shared between strings.</p></p>
Customer #531599 on COM-13716 - FemtoBuck LED DriverCustomer #531599urn:uuid:ac18fd7e-00f3-dd79-b4d7-5e3ac34e13332016-02-04T09:37:16-07:00<p>Can I connect a single FemtoBuck to a bunch of LEDs in parallel? Specifically 3watt LEDs that are rated at a forward current of 600-700mA? I prefer a parallel circuit to one in series to keep the voltage low, but what happens to the current requirement?
/---|>|----|>|----|>|-----\<br>
12V +--I---|>|----|>|----|>|------I--+<br>
---|>|----|>|----|>|-----/<p>Also, can the LEDs within the parallel branches that are in series be different? Thanks!</p></p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:fe20e150-2ffd-bdf9-723b-39a1050ada8c2016-02-01T09:27:36-07:00<p>You can hookup as many to one power supply as the supply can handle. They're about 95% efficient, which is to say, power out (Iout * Vleds) ~= 0.95<em>(Vsupply</em>Iin). Solve for Iin.</p>
Customer #215837 on COM-13716 - FemtoBuck LED DriverCustomer #215837urn:uuid:e6106263-a163-578b-0a88-52aea12b1eca2016-01-30T06:51:32-07:00<p>Can I hookup two of these from the same power supply? I want to be able to drive more than 8 LEDs with a 20V power source.</p>
--mi-- on COM-13716 - FemtoBuck LED Driver--mi--urn:uuid:ff6bde9b-9096-2fc2-1b74-20ec1e48e26a2016-01-28T16:06:22-07:00<p>This is my subjective observation - if I set manually PWM to 0 I got no light and when set PWM to 1 I got quite bright shining LED stripe. It is not important if this is 20% or 10% for me. For the current project I need to get soft start of the led stripe. This is the main purpose using FemtoBuck. It is not important if further fading out is linear either. I just got a black "hole" in brightness between 0 PWM and 1 PWM. I have no idea what could went wrong.<p>Michal</p></p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:98d3becd-291e-5b85-857b-546d977595c82016-01-28T15:04:10-07:00<p>How do you know 20% light output corresponds to 1 count PWM?<p>Light output behaves in a non-linear fashion; the output of this is linear, that is, the current varies from 0 to 350mA in equal steps as you go from 0 to 255. <a href="http://electronics.stackexchange.com/questions/1983/correcting-for-non-linear-brightness-in-leds-when-using-pwm" rel="nofollow">Here's a StackExchange article about correcting for that</a>.</p></p>
--mi-- on COM-13716 - FemtoBuck LED Driver--mi--urn:uuid:5f84e1e1-2af1-0ce8-8a13-b6af932d1e232016-01-28T14:49:02-07:00<p>I have problem using FemtoBuck LED Driver. Probably I have made some stupid mistake. After connecting the device to Arduino UNO (same as it was shown in tutorial - the only diff is D9-->CTRL) and 12V led stripe I cannot obtain linear dimming. So PWM values are from 0 to 255 while light intensity values I get are 0% for 0 PWM, 20% for 1 PWM, 21% for 2 PWM.... 100% for 255 PWM. I am unable to get "soft start" - only rapid on (with 20% LED intensity).
Please help
Michal</p>
SFUptownMaker on COM-13716 - FemtoBuck LED DriverSFUptownMakerurn:uuid:fae38d1e-bb59-7f75-e6e2-9ed989b904d82016-01-25T11:34:23-07:00<p>I haven't tried it; I'm curious as to whether it would work or not, though. I feel like it might do some weird stuff; the fact that the two (or more) devices wouldn't be synchronized in frequency or in phase might mean that you'd get weird currents flowing in odd places.<p>That said, if your lamp specifies 24W at 12V, it is almost certainly not a bare LED, but a lamp designed to be attached to a 12V power rail. If that's the case, you don't need a buck driver, just a 12V power supply.</p></p>
A. Wiggin on COM-13716 - FemtoBuck LED DriverA. Wigginurn:uuid:bab862fa-68a9-47dc-2ec3-1ecab89243a42016-01-22T21:37:09-07:00<p>I was looking through the hookup guide and in the section titled "Connecting to an Arduino or Compatible Board" and it very clearly states "Note that the LEDs are wired separately to each FemtoBuck! This is very important; the output of each FemtoBuck must be completely isolated from any other!" So if I understand your question correctly, I think that wouldn't work.</p>
A. Wiggin on COM-13716 - FemtoBuck LED DriverA. Wigginurn:uuid:a9c63a57-e911-5657-2ac7-55311bf0917a2016-01-22T21:32:14-07:00<p>So after more datasheet digging I found that the CTRL internal resistance is 50 kOhm. Perhaps someone can verify my train of thought on this... since I = V/R = 2.5V/50 kOhm = 50 micro-amps? Is that the max current that would be sunk by the CTRL pin?<p>And further, my supply voltage is 19.5V, if I drop it down through a 3.3V linear regulator and then use that voltage to control the dimming, would the power dissipated in the regulator be Watts = V * I = (19.5 - 3.3) Volts * 0.00005 Amps = 16.2 * 0.00005 = 810 micro-Watts. Does this sound right?</p></p>
A. Wiggin on COM-13716 - FemtoBuck LED DriverA. Wigginurn:uuid:105fcf4d-78dc-9f05-bbfd-be5910a926e42016-01-14T22:28:47-07:00<p>Does anyone know how much current the CTRL pin sinks when using it for dimming? My supply voltage is ~20V so I want to know how much power will be dissipated when I drop it down to 5V.</p>
Customer #129718 on COM-13716 - FemtoBuck LED DriverCustomer #129718urn:uuid:3c572bfc-c24a-e55b-f1dd-10b056e017c82016-01-11T18:49:53-07:00<p>I've got a couple of these boards, they work great, very pleased. I have a particular application where I'd like to drive an LED fixture using these boards. The fixture has two channels: one blue, one white. Each channel is spec'ed for 24 watts max at 12v. I'm constrained to stay at the 12v voltage level in this application, so at least 2A would be needed per channel. Since the femtobuck can drive up to 660mA, would it be feasible to run 3 or 4 femtobuck outputs in parallel to drive a single channel? I'm very curious if this would be a suitable idea or this is merely a terrible, horrible, & foolish idea. Thanks fellow Sparkfunians!</p>
Customer #129718 on COM-13716 - FemtoBuck LED DriverCustomer #129718urn:uuid:246f54b8-824f-8440-5aa7-c3c1415c80b62016-01-11T18:32:20-07:00<p>Looks like the link got moved to https://learn.sparkfun.com/tutorials/femtobuck-constant-current-led-driver-hookup-guide-v12</p>
Customer #693354 on COM-13716 - FemtoBuck LED DriverCustomer #693354urn:uuid:1b1c9882-68cb-dc26-d1b9-517e40d437b82015-12-11T10:45:10-07:00<p>"Hookup Guide" link:<p>https://learn.sparkfun.com/tutorials/femtobuck-constant-current-led-driver-hookup-guide-hi-power-version</p><p>is broken.</p></p>
Quazar on COM-13716 - FemtoBuck LED DriverQuazarurn:uuid:56b58948-26f2-3167-3216-60c3340f48bc2015-12-11T10:33:53-07:00<p>Nice looking little board, and just the thing for a landscape lighting project I've got in mind.<p>One thing to consider for future board revs: Add a couple more solder jumpers so the resistors can be configured in series as well. That would provide a 3rd current option of ~167mA without requiring any additional parts.</p></p>