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firepick-delta / firepick-delta

Design and Manufacturing Specifications for FirePick Delta
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LED ring lights may be too dim -- need weigh-in from the beta test kit owners #10

Open FlyingLotus1983 opened 9 years ago

FlyingLotus1983 commented 9 years ago

Affects the ELED01 and ELED02 PCB's. Could use suggestions from beta kit users that have resistors on-hand to try different values that don't exceed the specs below. We would like to know what lighting level you have in your designated FPD / SMT area, and how does the PCB look with the stock resistors, or other values?

ELED01 (down-looking end effector board)

Note: Use the down-looking camera and a circuit board on the bedplate. If there's glare, the values might be too bright. If the image is too dim, then the values need to be higher.

ELED02 (up-looking camera board)

NOTE: Use the up-looking camera to look at a large-ish part suspended on the tip of the nozzle, preferably an integrated circuit. We want the pads to be as WHITE as possible, and the IC body and background to be as DARK as possible. This makes computer vision easier.

Please attach or link pictures of what you see with the camera. You can use OpenPnP or a camera utility to take the pics.

cdsteinkuehler commented 9 years ago

I think you've got the specs backwards, the white LED has a 3.2V (typ) forward voltage and the red LED has 1.8V. Given there are two LEDs in series, it seems amazing if the white LED board lights at all (given a combined typical forward voltage of 6.4V)! The values for the red LED board seem a bit small if you want 10 mA (the value given yields a typical forward current around 13 mA, 150 ohm should yield a bit under 10mA at 5V). If you want to run the white LEDs off of 5V, they need to each have their own current limiting resistor of around 100 ohms (for 20 mA forward current)...or the existing 120 ohm parts would work well if there weren't two white LEDs in series.

For a short-term fix, I suspect if you simply short across every-other white LED, you'll get much more light output than with the existing circuit. This should be easy to test, but I don't have the parts to build an LED board, and I didn't get an assembled one in the bare-bones kit.

FlyingLotus1983 commented 9 years ago

Thanks Charles, you're right, I've corrected my initial post with the correct voltages.

If you'd be interested, I could supply you with the red / white LEDs and the 2x BSS138's if you'd be willing to help us with this issue. I'll mail you the parts free of charge (we have enough of them on a reel, lol). As for resistors, I recommend this guy: https://www.adafruit.com/products/441 Great tool for any hardware guy's arsenal.

cdsteinkuehler commented 9 years ago

Send me the LEDs and FETs, the resistor's I've already got on-hand (all 5% and 1% values between 1R and 10M in 0603 and 0805). Sometimes it's handy to design electronics for a living! :)

IMHO, the LEDs probably ought to be run off 12V if possible, particularly the white ones. It's hard to drive that many white LEDs with only 5V w/o wasting a lot of power (unless you're using "smart" switching drive circuits to regulate the current instead of plain old resistors). Quick back-of-envelope calculation shows if you assume 20 mA LED drive, you're burning 1W in the LEDs, and 600 mW in the resistors at 5V, or enough you probably need to think about things getting warm.

Charles Steinkuehler charles@steinkuehler.net

FlyingLotus1983 commented 9 years ago

We're using an ATX power supply for the resistors, sourcing current on the 5V rail won't be a problem. Putting it on 5V makes the wiring a lot easier, but I agree that it isn't ideal to drive LEDs with it.

On Saturday, May 30, 2015, cdsteinkuehler notifications@github.com wrote:

Send me the LEDs and FETs, the resistor's I've already got on-hand (all 5% and 1% values between 1R and 10M in 0603 and 0805). Sometimes it's handy to design electronics for a living! :)

IMHO, the LEDs probably ought to be run off 12V if possible, particularly the white ones. It's hard to drive that many white LEDs with only 5V w/o wasting a lot of power (unless you're using "smart" switching drive circuits to regulate the current instead of plain old resistors). Quick back-of-envelope calculation shows if you assume 20 mA LED drive, you're burning 1W in the LEDs, and 600 mW in the resistors at 5V, or enough you probably need to think about things getting warm.

Charles Steinkuehler charles@steinkuehler.net javascript:_e(%7B%7D,'cvml','charles@steinkuehler.net');

— Reply to this email directly or view it on GitHub https://github.com/firepick-delta/firepick-delta/issues/10#issuecomment-107079771 .

Neil Jansen, Co-Founder Tin Whiskers Technology, LLC http://tinwhiskers.io

BETZtechnik commented 9 years ago

Yes, I have to agree, the source voltage is too low for two of those in series.

Can you post the part numbers of the capacitor and mosfet as well so I can look at supplying the board with 12VDC?

I will also try out Charles' suggestion of using a 0 ohm resistor over one of the LEDs and see what the light output is with half the LEDs, but powered properly. And I think 120 is too low, and will cause current to flow in excess of the maximum. I calculate 180 ohms for 10mA.

Peter.

FlyingLotus1983 commented 9 years ago

MOSFET is a standard BSS138 (We used a Fairchild part, digikey P/N is BSS138CT-ND).

Capacitor is a pretty standard electrolytic 16V, 6.3mm diameter, around 100 uF.

Powering the boards with 12V is possible, but the wiring gets a little uglier.