LM3914 --help :/

Hi all!

Could someone explain me how does design from page 12 of

works.

Why all the LEDs are blinkink while the last one begins to lighth ??

Best regards

DM

noise, make sure you add caps to filter the VCC and input rw

no the it blinks as it should in that configuration shown on 12th page, but i do not undrestand why it blinks ...the idea ...could someone easely explain that ?

David

ok, now change the voltage on the input and you should see different led's turning on and of. The blinking led's mean noise on the input voltage. rw

ok now after reading you question again I understand what you mean. I did use this display, thats why I answerd. The blinking is controlled by the mode pin. see page 7 (and 8). I only used it dot mode as an amp-meter. rw

i have read p 7 and 8 and it doesn't say anything bout blinking :( i thionk that blinking is controlred by feedback capacitor but m not ssure .. what do u thing bout that?

david

take a look at pa 12 design with alarma flasher that ios what i am talking bout, but i do not understend the idea of blinking :(

look at page 7: Mode Pin use. Dot display: leave the mode select pin open Bar graph display: Wire Mode Select(pin 9) directly to pin 3 next: Dot or Bar mode selection, gives you details on what the mode pin does. Hope this helps rw

The REF OUT pin is also used to set the LED driver current. The LED driver current is about 10 times the program current out of REF OUT. When the last LED is enabled, C1 couples the cathode voltage to REF OUT through a resistor. This provides positive feedback, creating an astable multivibrator.

Increasing the LED current moves the driver pin towards ground, which further increases the program current because of C1 coupling. Eventually this saturates and current through C1 drops. Once out of saturation, LED current drops and positive feedback continues until the LED driver is shut off. As C1 charges to the new state eventually the program current increases and a new cycle begins.

Jack Rouse