I need to cut a 12v line to 9v for a circuit that I am picking up that is designed to run off of a 9v battery input, can anyone tell me how this is done?
LM7809 + 9 volts.... simple way, +12 in one lead, +9 out another. here is another way: http://www.uoguelph.ca/~antoon/circ/ps-lm317.html
That circuit will run just fine on 12V. LED current will go up from 2mA to 3mA, which won't hurt anything. The Maplin catalogue says "Requires an 8 to 15V power supply or a 9V PP3 battery (not included)."
I'm actually planning on desoldering the currently installed LED's and replacing them with UV LED's on some wire extenders. Effectively this will be a controller board for LED's mounted over a wider area, with the wires feeding back to this device. So, if the LED's are these: http://www.lsdiodes.com/shop/index.php?main_page=product_info&cPath=2&products_id=29 And I have a strong suspicion that I'm going to have to change the inline resistors for each LED... how would I calculate what I need to move the resistors to? If the input voltage has jumped from 9v to 12v, would that not also change the voltage @ the LED's? or is the voltage the same @ the LED and it is cut down to what is needed by the resistor? Guess I'm just trying to figure out the easiest way to make this board work with the LED's linked above in place of the installed red LED's, and I'm tripping over what the voltage and current will be @ the LED solder point. Make sense?
12V to 9V I had the same question, answered here: http://forums.bit-tech.net/showpost.php?p=1052559&postcount=8 Thread: http://forums.bit-tech.net/showthread.php?t=96991 I ordered the bits from - www.bowood-electronics.co.uk (Home » Semiconductors » Voltage Regulators - Fixed » REG108) The cap is optional.
LSDiodes show those as 3.3V forward voltage, compared to the 2V LEDs you're replacing. Current at 12V with the 3k3 resistor shown is (12V-3.3V)/3300 = 2.64mA. Straight LED swap OK. The reason Velleman are using such low LED currents is the CMOS CD4015 chip. Without adding some transistor current-boosting the chip can only supply a few mA to any LED. Luckily, LEDs glow well on a few mA, they don't need 20-30mA unless you're after a torchlight.
Ok, I'll try the straight swap. Hopefully this will be enough to light the LED enough to push its UV effect through some UV reactive acrylic. Thanks again cpemma! Dunno what I'd do without you and your knowledge!
If you're extending the LED leads anyway, it wouldn't be a great deal more effort (or expense) to use a ULN2803A chip to boost the LED current. A wire from the original LED anode pads to each of the 8 inputs (the existing 3k3 resistors won't affect things), 12V--330R resistor--LED-- to each of the chip's 8 outputs, and a ground to the chip's ground pin.
I have the UV LEDs from LS and they do not produce very much UV light. Very reactive materials glows nicely, but most do not. The only way I could get the materials to glow was NOT difusing the light and "spot lighting" the effect closely. You would be better off with a UV CCFL. I understand that they won't sequence very well, but I caution you to try the LEDs first before buying the circuit. Hope this works for you. Love to see pictures of what you are building.
The kit is not built, I'll have to put it together. That being said, would a resistor change near the LED's make this any easier on any level? I mean, in conjunction with your suggestion, something to add a bit of current and enough voltage to make the LED's stand out. The more I think about this, the more I am contemplating just making my own.... but the idea of a pretraced circuit board appeals to my very basic soldering skill set!
The thing that always bothers me about people on this forum is that everyone is always wondering about this resistor VS that resistor. Whenever i'm working with leds, at any voltage below about ~24 v i just use 1k resistors. It requires soooo much less thought, and the difference between a led at 5ma and 20 ma is very small. Plus, it's much harder to destroy your leds. The bottom line is, don't worry too much about the led resistors unless you're doing something like trying to build a flashlight.
You're right. Though in this case, Tech-Daddy is after maximum light output to make the acrylic glow. Incidentally, one minor snag with the running lights kit is that on power-on, all the leds are off. You have to keep pressing the PROG button until you get the effect you want (and it doesn't remember the setting after power-off). But a good cheap kit to practice your soldering on (£5.99 from Maplins).
Excellent link cpemma! Thank you for your input! Always appreciated! I'm going to try some experiments between the UV and a white LED. I'm going for a similar effect as what was used on the X-Fi guitar amp mod showcased here @ bit-tech, except with a different twist.... So, I may be able to get the same visual effect that I'm looking for with white as with UV. I just need to see who needs less to run with to get optimal lighting. Thanks again for your assistance!
