MintyBoost LEDs

Ideas and questions about MintyBoost kits

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aclight
 
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MintyBoost LEDs

Post by aclight »

I just finished building my MintyBoost and added the optional surface mount LEDs. Since I didn't see exact instructions on this board for what parts to use, I thought I'd share what I used in case someone else is interested in trying this.

All part numbers below are DigiKey numbers.

R1: 100KOhm resistor, SMT 1206 package size, Cat#541-100KECT-ND, $0.39 for 10
R2: 110KOhm resistor, SMT 1206 package size, Cat#RHM110KFCT-ND, $0.47 for 10
R3: 220 Ohm resistor, SMT 1206 package size, Cat#RHM220FCT-ND, $0.47 for 10
LED: red high intensity, SMT 1206 package size, Cat#P11532CT-ND, $5.90 for 10

The resistors can be mounted in either direction. The LED has to be mounted in a certain direction. With the mounting surface of the PCB facing up, and the LED's towards you, you want to mount the anode (+) on the left and cathode (-) on the right. If you buy the LED specified above, look at the bottom (opposite of LED face) side and there is a small diagram. The fat end is the anode side, the skinny bar is the cathode. Soldering on these pieces isn't easy--I had the help of a high powered binocular microscope and fine forceps. I put down a dab of solder on each pad first, then placed the component on top, and then pushed the component down with the forceps while applying heat to the solder already on one of the pads. Once that melted, I switched sides and went back and forth until the component was set right.

Don't forget to drill a hole in the bottom of your case so you can see the LED.

An easy way to test if your LED is working is to put both batteries in the holder for a few seconds, and then disconnect the circuit (by pushing one of the batteries towards the spring so that the (+) contact of that battery stops contacting the pad in the battery holder. You should see the LED light up briefly (~1 second) as the capacitor discharges. Then the light will turn off.

I hope this helps you out.

Happy boosting
AC

adafruit
 
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Post by adafruit »

great! thanks for the tips :)

fever16
 
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Post by fever16 »

nice
can u post some pics ,so that it could be clear

aclight
 
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Post by aclight »

I don't have a camera right now.

What's not clear? The components are so small that I'm not sure how helpful a picture would be.

AC

aclight
 
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Post by aclight »

Ok, I finally was able to get a camera to take some photos. They aren't great, but I think you can at least get the idea.

They are at http://picasaweb.google.com/aclight/MintyBoostPCB/

Note that I am now using a 110K and 100K resistor stacked in parallell for R1, instead of a 100K ohm resistor as I said originally. This gives a net R1=52K ohm, which sets the low battery indicator voltage to a (I think) more reasonable 1.9V.

I should also say that I can't get any of my minty boost's to work (with or without LEDs), and though I'm not claiming that the LED circuit has any thing to do with the boards not working, just keep that in mind if you add LEDs and your board stops working properly.

AC

dbk
 
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Surface Mound LED

Post by dbk »

Can a regular LED with component leads be used instead so that the indicator light can be placed anywhere in the case via wires etc.? If so, what specs on the LED are needed, or is any LED O.K. ??

Does RadioShack sell surface mount resistors??

dbk
 
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Low battery Indicator

Post by dbk »

Has anyone had success with this implimentation of the MintyBoost?

I tried to get it to work and it seems to get the LED to light at about 1.8v but after this it no longer charges my iPod when it had been working fine.

I will undo the resistors and let you know if it starts working again.

aclight
 
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Post by aclight »

What value of resistor are you using for the LED part of the circuit? Maybe your LED is just drawing too much current and there isn't enough left to operate the converter chip and so it stops charging.

adafruit
 
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Post by adafruit »

should still work.... (?)

dbk
 
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LED

Post by dbk »

Yes it does work now. Not sure what the problem was.

BobCochran
 
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Green LED, Green Bar

Post by BobCochran »

Solder your SMT parts on first. Install the through-hole parts after the SMT parts.

I happened to have a green LED in 1206 casing, and that has a green bar or a green stripe at one end. The end without the green bar or green stripe is soldered to the pad closest to the resistor R3. I hope I got this right - I haven't tested to see if the LED will light up. I just happened to have a 330 Ohm resistor so that is what I used for R3.

The 100K resistor can have a marking '104' on the case. The 110K resistor can be marked '114' or '1103' on the case. Be sure to test the resistance with a multimeter if you are unsure. It's easier than desoldering the wrong resistor size.

If you need to desolder an SMT component, the easiest way to do this is with two soldering irons. Heat them up, then put the tip of each iron on each end of the component you want to remove. When the solder on both pads liquifies, gently lift the component up off the pads with the irons.

Be sure that the MintyBoost PCB is firmly gripped in a vice before doing this otherwise you might simply push the board into an awkward angle unexpectedly.

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moses_410
 
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Post by moses_410 »

hey aclight, if i use the resistors stated above (R1: 100K; R2: 110K; and R3:220K) at what voltage will the light go on? and at about what voltage would the batteries be considered 'dead' and no longer charge a USB device? Thanks.

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moses_410
 
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Post by moses_410 »

nevermind, its about 2.4 v.

Ladyada, are these the correct value resistors and led you would recommend? (R1: 110k and 100K R2: 110K and R3: 220K) ???

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