Archive: 4 posts

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There is one thing I don't understand about logic probes And that is, how does it detect numbers below its first digit Let me explain, if you want to detect 2.3 then detecting 2 is easy with a sequencer, but how would you detect 3 besides having to make a sequencer with like 1000 batteries? I really don't get how to get past the 2nd digit barrier (or any of the others for a matter of fact)

2013-12-10 15:46:00 Author: amiel445566 Posts: 664

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The idea behind how a logic probe works can be summarised as follows. Lets say you want to detect the signal 23.107% We can detect the first digit "2", quite easily (as you say) by just using a positional sequencer with 9 batteries which represent 10%, 20%, 30%, ...., 90%. We can set these batteries to different have values as follows; the battery to represent 10% should have a value of 10%, the battery to represent 20% should have a value of 20% etc. If we then feed all of these 9 batteries into an OR gate it logically follows that if our input signal (23.107% in this case) is between 10% and <20% the OR gate will have an output of 10%, if the signal is between 20% and < 30%, the OR gate will have an output of 20%, if the signal is between 80% and <90%, the OR gate will have an output of 80% etc. (Refer to Figure 1). Figure 1 - 47453 In this example, with the signal being 23.107% the 20% battery will be activated on our positional sequencer, this will feed into our OR gate and so our OR gate's output will be 20%. We can then subtract this from our initial input signal with a direction combiner: 23.107% - 20% = 3.107% Now lets simply multiply this signal by 10 to obtain the signal 31.07% (Refer to figure 2). We can multiply a signal by 10 by simply adding the signal to itself 10 times. Figure 2 - 47454 Below we can see a side by side comparison of the input signal to the output signal for this logic set-up (Refer to figure 3). Figure 3 - 47455 We can now easily detect that the 2nd digit is a "3". Further iterations of the above process will allow us to continue to accurately detect the value of the signal. The more iterations we perform of this process, the more accurately we describe the signal. There is one small issue with the above logic which can be seen below (Refer to figure 4). Figure 4 - 47456 Here we have a 10% signal as our input but we see that the 10% battery is not active on our sequencer, this will cause major problems. To fix this problem we will use what is commonly referred to as a "fudge factor". The fudge factor is a small signal which we will add to our input, so rather than 10% our signal will now be something like 10.0001%. The set-up below (Refer to figure 5) shows an inverted timer with max-time 1000.0 and current time 0.1, the timer's output signal will be (100 - 0.0001)%. In this set up we see our input signal (10%) is subtracted from the timer's signal which yields the following: Figure 5 - 47457 Direction Combiner Output = 100 - 0.0001 - 10 This then feeds into a NOT gate to yield: NOT Gate Output = 100 - (100 - 0.0001 - 10) = 100 - 100 + 0.0001 + 10 = 10.0001 This signal will then feed into our sequencer. Because our signal is now ever so slightly larger than 10% it will activate our 10% battery. This will NOT cause the logic probe to be incorrect by 0.0001. Beyond creating a digital number display that's all there is to it, if you have any questions feel free to ask and I'll do my best to make everything crystal clear.

2013-12-12 09:53:00 Author: Seku Posts: 65

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The set-up below (Refer to figure 5) shows an inverted timer with max-time 1000.0 and current time 0.1 I'd suggest using a timer with a target time of 12,000.0s and setting the current time to 1.2s, if you're really trying to be accurate. Due to the fact that timers add or remove a frame for certain times. See: http://wiki.lbpcentral.com/Talk:Timer I don't remember exactly how I sussed it out, but I think 12,000.0s seemed to work for me. It's been so long that I can't remember if this is even accurate. Certain timer values do indeed have a missing or added frame, though. After thinking about it more, I suspect that 0.9 / 9000.0 might work as well. Unsure.

2013-12-12 13:22:00 Author: comphermc Posts: 5338

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Thank you all so much, with your help I have been able to recreate my own version of a Logic Probe, with modular logic sets inside, I will be uploading it to my earth soon in a giveaway if you want to check out exactly how I did it Again thanks for the help

2013-12-13 05:40:00 Author: amiel445566 Posts: 664

Posts: 1077139    Threads: 69970    Members: 9661    Archive-Date: 2019-01-19

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