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46  Using Arduino / General Electronics / Re: DIY PCB transfer media on: January 15, 2013, 01:29:16 am
Definitely looks promising. I'll have to try this one out. Just have to find this vinyl stuff locally.
47  Using Arduino / General Electronics / Re: DIY PCB transfer media on: January 14, 2013, 04:06:38 pm
How well does it work for thin pitch? (0.5mm) The problem I have with my photo paper is that with fine picthes (less than 1mm) the photo paper gets transfered and stuck in between traces along with the toner. I end up having to scrape in between traces with a knife.
48  Using Arduino / General Electronics / Re: LM317 CC/CV circuit not working on: January 12, 2013, 01:10:24 am
Hmm, they did work when I first tested them after noticing the problem. And I was pulling 500 mA from all of them. Now 2 of them give 6v when set to 5v and one gives 4.8v. I can only pull, guess how much, 7 mA now. Do they usually die this quick or did I get fakes? Who knows. I guess I'll include some in the next Digikey order.
49  Using Arduino / General Electronics / Re: LM317 CC/CV circuit not working on: January 12, 2013, 12:44:41 am
Is this a common failure mode of the LM317? I tried the simple 1 resistor CC circuit and also got about 7 mA no matter what. To be fair, I'm pretty sure all three of these LM317's have been soldered in backwards before in other circuits... I'm not good when it comes to checking the orientation.

EDIT: I'd appreciate it if someone built a simple CC circuit with a 47 ohm resistor and used a 1k resistor as the load. What voltage do you get across the 1k? current through it? I should be getting 26 volts (higher than my supply voltage) instead of 4 volts, and 26 mA instead of 4 mA.

FWIW: with adjust grounded, I get 640mV on the output. Not good?
50  Using Arduino / General Electronics / Re: LM317 CC/CV circuit not working on: January 12, 2013, 12:22:07 am
I get 4.2 volts either side of the resistor with no load. I even tried various values from .1 to 47 ohms and got the same results. I'm no master at LM317 circuits, but if I remember correctly, voltage is controlled by the amount of current going into the adjust pin. I believe the voltage divider (R4 and R5) allow the TL431 to conduct or not conduct depending on output voltage, therefore regulating the voltage if R1 and R2 don't drop it enough (ie. if the current is lower than that set by R1 and R2).

Maybe that means that the TL431 isn't allowing enough current to flow into the adjust pin? What I'm really confused by is R3. What does it do? Removing it makes no noticeable difference.
51  Using Arduino / General Electronics / Re: LM317 CC/CV circuit not working on: January 11, 2013, 09:58:03 pm
At 1000 ohms it's still in constant voltage mode... Go take your wisdom elsewhere please. And I get the same results with a battery instead of a resistor.
52  Using Arduino / Project Guidance / Re: How do you make the current draw from a device gradual instead of instant? on: January 11, 2013, 09:43:32 pm
I've seen it done like this before. First your load receives power through a 1 ohm resistor (fiddle with the value) and the capacitor slowly charges up to the relay turn on voltage. Once the relay latches, it and your load receive full power since the resistor is bypassed. Make sure you use a high wattage resistor.
53  Using Arduino / General Electronics / LM317 CC/CV circuit not working on: January 11, 2013, 09:23:37 pm
I built this circuit ( about a year ago and I remember that it worked fine. Recently I built it again but this time I'm having some problems. No matter what value resistor I use for R1 and R2 (currently combined into a 1 ohm resistor), the constant current always kicks in at about 7mA. In the attached picture, good.bmp, ch.1 is output voltage and ch.2 is the reference pin on the TL431. The output load is 1000 ohms and as you can see, it works as it should. In the picture, bad.bmp, the output load is 500 ohms and obviously something isn't right. I've tried 3 different LM317's and TL431's (actually 2 of them are KA431's) and I get the same results with all of them. R5 is a 50k potentiometer and R4 is 56k resistor. I have 100uF on input and output. Any idea what could cause these results? The input voltage stays at a steady 16v and nothing gets warm.
54  Using Arduino / Displays / Re: need fast lcd on: January 11, 2013, 04:30:10 pm
The shields usually contain a 5 volt to 3.3 volt converter for the logic signals. Unless you are using a 3.3 volt arduino, you'll need the extra board.
55  Using Arduino / Displays / Re: SOLVED-BIG 7 inch TFT Looks great- 1 issue. on: January 10, 2013, 04:20:49 pm
Glad I could help. Setting register 0xB0 to 0x04 instead of 0x24 enables 18-bit mode instead of 24-bit mode. These LCDs typically have 18 data lines, although only 16 of them are usually broken out onto boards. Since you originally had 24-bit mode enabled, the LCD was looking for at least 2 data writes. When you switched it to 18-bit mode, it looked in register 0xF0 to see which interface to use: 5,6,5 RGB in this case.
56  Using Arduino / Displays / Re: need fast lcd on: January 10, 2013, 02:06:59 am
The SSD1289 (and probably most other similar controllers) can also be run in 8-bit mode instead of the full 16-bit mode usually used if you're really tight on I/O
57  Using Arduino / Displays / Re: BIG 7 inch TFT Looks great- 1 issue. on: January 09, 2013, 09:40:55 pm
I don't know much about TFT's nor the SSD1963 so this is really a shot in the dark, but if it's anything like the SSD1289 then you might be initializing it incorrectly. Take a look at page 71 in the SSD1289 datasheet ( It shows that you can use 262k and 65k color in 16-bit mode. Perhaps you're initializing it in one of the 262k color modes? That way the display would receive what it thinks is the red and green data, then presumably you would send a command to move to the next pixel and the blue data would never be received. Seeing as the library already had other errors (the rotation) this could be a likely possibility. I'm not sure about the whole B,G,R vs. R,G,B though.
58  Using Arduino / General Electronics / Re: Soldering Hell on: January 09, 2013, 04:02:56 pm
I would definitely recommend using extra flux. Ever since I started using flux I've never had a problem with wetting.
59  Using Arduino / Displays / Re: SSD1289 frame buffer on: January 03, 2013, 12:26:12 am
Also how would I go about doing IO in assembler? For example, let's say I want to put 0x00 on port E. AVR seems to have a convenient OUT instruction which ARM cortex M4 doesn't. Couldn't I just MOV 0x00 into the output data register of port E? the output data register of port E on my MCU is 0x40021014 but I have no idea where to go from there.

EDIT: ok I figured it out. Turns out all my values have to be in registers and I actually use LDR and STR. I don't understand why I can't replace R3 in the STR line with 0x0. Code for future reference:
asm("ldr R1, =0x40021000");//pointer to GPIOE base
asm("ldr R3, =0x00000000");//to set all bits low
asm("str R3, [R1, #0x14]");//store R3(0x00) into R1(GPIOE_base) + 0x14(ODR)
I don't think it will be much faster than doing it in C though.
60  Using Arduino / Displays / Re: SSD1289 frame buffer on: January 02, 2013, 09:34:08 pm
STM32F407VET is the MCU. One frame is 320x240x16/8 = 153600 bytes. the MCU only has 192KB of RAM if I remember correctly, which doesn't leave much room for other non-LCD related stuff. I'm thinking about adding external RAM but I'm not sure how fast that will be.
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