DPRG List

 [DPRG] anyone can explain?? Message index sorted by: [ date ] [ thread ] [ subject ] [ author ] Previous message: [DPRG] avr Next message: [DPRG] avr Subject: [DPRG] anyone can explain?? From: DeltaGraph at aol.com DeltaGraph at aol.com Date: Sun Jul 17 09:05:43 CDT 2005 ```NOBITA There are a number of people on the list that could look at this circuit and tell you almost instantly how it works, and maybe someone will. I am not sure how much that would help you other that to solve your immediate problem. This is not a trivial circuit. My approach is divide and conquer. 1. I looked up spec on LM393 to find out it can only sink current. Typical of comparators I think. That is when "ON" (+ input voltage greater than - input voltage) the outputs are pulled near ground when "OFF" 2. Think about what is happening when ComA is ON (output tied to ground) and when not. (Sketch those cases if you need to -- that will help a bunch 3. Ohm's law needed to find ComA V+ (and ComB V-) You can solve for what those voltages will be for each state of ComA output using simple series and parallel combinations of resistors and Voltage Divider Rule. Search internet for "Voltage Divider Rule" or "Resistor Series Parallel" 4. Look at how the comparator's output state (ON or OFF) changes the configuration of sources (ties to +4.5) or sinks (ties to GND) of the series RC circuit which is the key to how fast the circuit switches. I searched internet for "RC circuit charge discharge" and instantly had a bunch of pages and sample JAVA scripts to show me formulas... sample graphs ... 5. Notice that ComB does not affect the timing of the circuit, but its threshold is modified by the state of ComA Your capacitor is fixed at .1uF but the series resistance tied to either +4.5 or GND depending on comparator output state is changing. You can find formulas that will tell you how long that will take. Now with this information, I would suggest you figure out how the circuit works -- or you could just adjust the pot and see what happens. You could use either a scope or you could test with target sensor to see when the circuit is tuned. Another suggestion would be to study or find a discussion of how a 555 timer works. That might just help with understanding of this circuit. - Ron Grant -------------- next part -------------- An HTML attachment was scrubbed... URL: http://list.dprg.org/pipermail/dprglist/attachments/20050717/aaa755ed/attachment.html ``` Previous message: [DPRG] avr Next message: [DPRG] avr Message index sorted by: [ date ] [ thread ] [ subject ] [ author ] More information about the DPRG mailing list