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  1. Hi All, I'm looking for a cheap and easy way to transfer my circuit onto copper board. I'm using a piece of software that can print the tracks 1:1 on a printer. I'm aware of the various methods out there, photoboard+UV light, transfers, laser printer/toner method, etch-pen, etc. I came across a paper product that allows you to print a graphic using an inkjet printer and transfer it onto a T-shirt using an iron. Would this work? Has anyone has tried this? Thanks, Salvatore.
  2. Hi audioguru, I've checked the datasheet for the LM311 and according to the Electrical Characteristics table the response time is 200nS given a 100mV input step and 5mV overdrive(?) which appears to be the very much the same as the LM6511 which has a 180nS response time with a 100mV input step and 25mV overdrive, again as indicated by the Electrical Characteristics table. I found the graph you attached in the LM311 datasheet, but I also found one ( see attached ) that appears to show that the LM311 is capable of much faster switching and which also ties in with the values that the table shows.
  3. Hi, Will this circuit work ( see attached )? I've determined that the worst case scenario is that a 1uS flash of light needs to be detected with a 66us delay before the next flash. Once I get this last problem nailed down I can build my board! SFH2030F.pdf
  4. Great! There's the SFH2030 that has a rise/fall time of 5nS! Currently the phototransistor in my circuit is supplied with 5V and acts as an input to a LM311N comparator. Can I use the photodiode as a drop-in replacement for the phototransistor or will there be issues I need to address? Thanks, Salvatore.
  5. Hi, I'm using a phototransistor ( SFH300-3 ) in my circuit that has rise/fall times of around 10uS. I need a phototransistor that will respond to 2uS or quicker pulses of light. When the manufacturer specifies a rise time for example, does this mean that the phototransistor has to be illuminated for this length of time for it to reach it's full gain given a certain voltage drop and illumination? Or, will it respond to shorter length pulses, where the rise/fall times are just reaction times and that the full gain will eventually be reached after the rise time has elapsed? If this isn't that cas
  6. Couldn't you use a comparator that takes both inputs. When the output is zero, the signals are at the same voltage, i.e. 'crossed', then all you have to do is to take a reading from one of the inputs for the actual value.
  7. Hi, If you can determine what values for R1/C1/C2 I need to solve the problem please let me know! :D Will the cmos inverters just invert the signal? If this is the case then it won't solve the problem as a
  8. Hi, I think I've found the problem! :D There's a formula in the datasheet for determining the maximum frequency that can be input: Fmax=I2/C1*Vcc=0.00018/(0.0000000047*7.57)=5060Hz. At this frequency, the half cycle pulse width would be 0.098ms which from my testing turns out to be just about the value that I determined was starting to give me problems. So the only solution I can see is to increase the pulse width at source, i.e. somehow delay the pulse generated by the phototransistor so that it remains a constant at around 0.1ms regardless of the input frequency or duty cycle. Anyone know ho
  9. Hi audioguru! I remember you helping me out on my comparator problem!
  10. Hi All, I've almost finished my project for a tachometer circuit. Testing went well until I appear to have hit upon a snag for which I need some help. It concerns the LM2917N frequency to voltage converter IC, which I can happily 'program' to give the correct output with a given frequency input ( 0-2500Hz ) using a frequency generator. The problem arose when I tried to vary the 'duty cycle' of the input frequency ( which is a square wave ), i.e. I adjusted the 'HI' time to make it a smaller percentage of the time 'LO'. Whatever frequency I input, if I adjusted the HI so that it was less than 0
  11. Hi Again! ;D Following on from the problem with the comparator ( which is now solved, thanks! ), I've since progressed with my circuit and have managed to get things more or less working. This sub-circuit is ultimately to act as a light detector ( using a laser diode as the light source ) to serve as input to a larger tachometer circuit measuring frequencies up to 2500Hz. The output of the comparator will be fed into the HCF4018B CMOS divide-by-N IC which will function as a first stage frequency divider. I've attached a schematic of the light detector, the blue and red parts depicting alternat
  12. Hi All, Well after all that, it turns out that the 1K pot I'd replaced the 1M pot was in fact also a 1M pot... doh..!!
  13. Hi, I've attached a schematic ( I hope! ). I've changed the 1M pot to a 1K pot. Results are exactly the same as the previous tabulated results. Cheers, Salvatore.
  14. Hi, To keep things simple, I've reduced the circuit to not include hysteresis. I can't seem to find how to attach a schematic (sorry!), but the circuit is literally the LM393, +5V supply to the comparator and two pots, one 1Mohm for the -ve reference input and a 10K for the +ve input, all connected to ground. The output of the comparator has a 2K pull-up resistor.
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