PlaneCrazy
Member
I was hoping to avoid this.
I've been lurking on this forum for quite a while now, and I've joined a month or two ago. I am a mechanical engineer, but was recently assigned an electronics project since I have shown an interest in these things. Now I'm just getting depressed.
I have to make a fuel level indicator, so I found on this forum that I can do so using a lm3914 chip. I have ordered two of these and a 20LED bar, with several 1M and 10k resistors (10 of each), a few 2.2µF caps, and borrowed a breadboard. (She was kind enough to "forget to mention" the few 470Ω and 4.7kΩ resistors lying around with the breadboard.)
I tested each and every "row" and "column" of the breadboard for contact, mostly because I forgot how a breadboard is wired. I then connected the circuit as per the data sheet, applied a 12Vdc input over the chips, 6V with a 10kΩ pot to simulate the signal (which must ultimately be 0-5Vdc) and watched in awe as nothing happened. The LEDs have a driving voltage of ±3Vdc, which I obtained by dividing the 12Vdc with a 10kΩ and two 4.7kΩ and picking up between the 2 4.7kΩ resistors. I will draw a diagram if necessary, but instead I'm risking getting banned by requesting anyone with a heart to please, please, pretty please give me a complete, clear circuit so I can just bloody order the components and build the fuel level indicator. If there are things I would like to know ("how did you know what size resistors to use?", "where did you get those values from?", "calcs?") I'll ask, but right now I need results pronto.
I've searched using Google and "Search forum" and have read through many lm3914-related posts and threads, but I am not smart enough to decide which thread will help me the best. If you could recommend one of those, it'd be swell!
Apologies in advance. I'm seeking help from an actual electronic engineer, but first I have to find one...
I've been lurking on this forum for quite a while now, and I've joined a month or two ago. I am a mechanical engineer, but was recently assigned an electronics project since I have shown an interest in these things. Now I'm just getting depressed.
I have to make a fuel level indicator, so I found on this forum that I can do so using a lm3914 chip. I have ordered two of these and a 20LED bar, with several 1M and 10k resistors (10 of each), a few 2.2µF caps, and borrowed a breadboard. (She was kind enough to "forget to mention" the few 470Ω and 4.7kΩ resistors lying around with the breadboard.)
I tested each and every "row" and "column" of the breadboard for contact, mostly because I forgot how a breadboard is wired. I then connected the circuit as per the data sheet, applied a 12Vdc input over the chips, 6V with a 10kΩ pot to simulate the signal (which must ultimately be 0-5Vdc) and watched in awe as nothing happened. The LEDs have a driving voltage of ±3Vdc, which I obtained by dividing the 12Vdc with a 10kΩ and two 4.7kΩ and picking up between the 2 4.7kΩ resistors. I will draw a diagram if necessary, but instead I'm risking getting banned by requesting anyone with a heart to please, please, pretty please give me a complete, clear circuit so I can just bloody order the components and build the fuel level indicator. If there are things I would like to know ("how did you know what size resistors to use?", "where did you get those values from?", "calcs?") I'll ask, but right now I need results pronto.
I've searched using Google and "Search forum" and have read through many lm3914-related posts and threads, but I am not smart enough to decide which thread will help me the best. If you could recommend one of those, it'd be swell!
Apologies in advance. I'm seeking help from an actual electronic engineer, but first I have to find one...