I've also had nothing but problems with this mod I have built the circuit as shown here in the stripboard diagram here There's no problem with solder joints or bad stripboard tracks but the leds still won't light up. In fact...plugging in the fan+ & fan- connectors is almost suicide because it sends 12v out!! instead of allowing the variable input in to the LM3914, even stops the Fan spinning. All I need is a circuit that will display 4v to 12v (0.8v increments) using all 10 leds. BTW Gordy_Hand, do you really need a resistor between 12v & Leds? I thought the LM3914 regulated power to the leds? Also, does it make any difference to the LM3914 circuit if the signal is from a PWM as shown here I've tried using LM317 Circuits here & MIC29302BT based circuits here but it makes no difference....It still doesn't work!!!!! I don't really want to risk connecting it to my new PWM controlled fanbus incase it frys it.
Well its not entirely true the lighted once on the first circuit but when I played with the voltages they stopped working. The leds are still working fine tho . I think I am gonna scrap the stripboard and go to the breadboard layout from the orginal site as I know it should work. deedub I've no idea about resistors Also how do you know which is postive and negative on a capacitor ? Just so I don't blow another up
As far as I know There should be a negative sign on one side of the capacitors......Sometimes very difficult to see, especially on small Tantulams. If there's one lead shorter than the other then that one is usually the negative.:dude: BTW, hope your now deceased Capacitor put on a good Light Show! Let me know if you get your circuit working.
I couldnt see any difference in length and remember checking for a sign and lining it up . Oh and it was a light and sound show
What type of Capacitors are you using? Plus what kind of fan control are you plugging the circuit into? If if's a PWM Circuit then you might need to modify the schematic a little. LEDs will strobe at lower voltages in PWM circuits.......Quite a cool effect but probably not suitable for LM3914's.
I used the one suggested on page 2 And I'm using the circuit mentioned in my first post the top one on cpemma's website
I asume you mean the tantulam Capacitors....... Those should be fine LM317 based circuits are also fine, I just thought you may have been using a PWM setup......which i'm pretty sure will need a more complicated circuit:dude:
The black fan wire from a "low-side" PWM-controlled circuit like /51/ isn't at ground potential, connecting it to a true ground (0v) will effectively short out the PWM switching transistor so the fan will run full-speed all the time. On the tantalum caps, most have a + sign and stripe on the right-hand side (viewing the lettering), with some brands the positive lead is also longer.
Mine works :dude: Only change from the stripboard layout shown earlier was to (a) add a 4k7 resistor from pin 4 to ground, instead of the link. This raises the voltage to light the first led to about 5v. (b) this needs an extra track break on the pin4 row and a link from the fan ground (on the other side of this break) to supply ground (the row to pin2). (c) tidied the links up by hiding some under the preset. (Stripboard Magic won't allow this.) Front view (sorry about the quality, scanners aren't designed for this job ) And back side: With the preset pot, all the action takes place in the first fraction of track, with 12v input on the fan wires, hard anticlockwise, no lights will be on, turn up very slightly and the column grows. Tweak till the top light is just on. Another point, it's "upside down" as shown above, the upper led (from 3914pin#1) is the first to come on.
Cheers Cpemma, I'd all but given up on the Bar-Graph idea I'd like a 4v to 12v range so what resistor change would I need to the above? More Importantly.... what modifications do I need to make to this circuit to use it with a PWM based fan controller? As soon as I know I'll try this new schematic, hopefully it can be used with PWM:dude: Don't worry mate, I've seen alot worse.
No exploding capacitors for you then Pah your not trying Nice work , just a quick question I can't see what you've done with the led's on the right hand side is it connected to 12v ?
That dot on the bottom right of the leds is the end of a thin wire link running along all the anodes, then the link bottom left of the ic joins bottom row to 12v line by ICpin#9 I based on the internal resistor chain in the 3914, 9k above the first comparator, another 1k plus my 4k7 below so led#1 comes on at 12*5.7/14.7 = 4.65v. If that's right (and I've not checked with a voltmeter), then 3k9 would start at 4.23v, 3k6 at 4.05v. As far as getting PWM to work, I think you'd need a small NPN on the output followed by a larger PNP transistor (or p-channel mosfet) so the fan could go between transistor and ground. IIRC Tutorial Fan Speed Control is Cool! has some info on this, look for "high-side control". How the lights will react to a pulsed signal, f* knows, but the 0.47uF cap will give a bit of smoothing.
Thanks for the info mate. I'll check out the link tomorrow and see whats needed very nice! Actually I've already hooked up some hyper bright Blue's. At 12v there at full brightness.....BUT at 4v the LED's strobe BIG TIME!.......looks damn sweet:dude:
Checked out the site but I'm still unsure about how to combine PWM with LM3914's It would be good if they included a few built examples. I'm open to any sugestions BTW Cpemma According to that equation:- 3k9 resistor works out at 4.92v and a 3k6 resistor works out at 5.02v Wouldn't a 7k resistor bring it closer to 4v? (12*5.7/17 = 4.02v.) Unless I'm completely losing the plot now.
