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  • Not wanting to be un'nice', but this is one of those areas where - when you have to ask questions _here_, you will probably not able to do it. RF (especially in the GHz range) _IS_ black magic - that's from a radio amateur who designed testers for car phones for a living (by implementing testing equipment with a price tag that could have bought a small plane). Analog was bad - but digital? Urgh....No, just a receiver (and power measurement) from 200MHz to 2GHz won't help you. There is _A_LOT_ of stuff in between those phone bands going on (e.g. all terrestial television broadcast, avionics, radar ... all depending on where you live).This "favoriot" project? Yes, definitely something related to waht you wanna do. But orngrimm is very optimistic with his 80%. On the favoriot web...

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    Not wanting to be un'nice', but this is one of those areas where - when you have to ask questions _here_, you will probably not able to do it. RF (especially in the GHz range) _IS_ black magic - that's from a radio amateur who designed testers for car phones for a living (by implementing testing equipment with a price tag that could have bought a small plane). Analog was bad - but digital? Urgh....No, just a receiver (and power measurement) from 200MHz to 2GHz won't help you. There is _A_LOT_ of stuff in between those phone bands going on (e.g. all terrestial television broadcast, avionics, radar ... all depending on where you live).This "favoriot" project? Yes, definitely something related to waht you wanna do. But orngrimm is very optimistic with his 80%. On the favoriot website, they have error bars of 25dB. Looks good? Well, that's 31622% (for power)! About a factor of 320! And no, that is NOT a (very) bad value for power measurements. You'd need a least band pass filters for the three phone bands (depending on your area), a power detector circuit for all of them and then there is still the question of what you want to measure? Average emitted power? Peek emitted power? These tower emitt pulses of pulsed data and are quiet in between. So, it is tricky to define, what 'power' is in that case.Sorry, if that all was somewhat negative. But that is one of those problems that look easy from far away - any cell phone shows you the signal strength with its 5 bars - so measuring that can't be difficult - can it? Yes, it can. The phone _has_ dedicated receiving circuits and 5 bars is more like guessing anyway.

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  • Full, short answer: Anything. De nada.Longer answer:- far below 8.2? Should just not turn on. (May get hot, though - very unlikely)- a bit below 8.2? Optimal: may turn on, detect under voltage, inform you and shut down.Good: may not turn on.Bad: may turn on and show (slightly?) wrong measurementsFatal: may self destruct (unlikely)- a bit above 9.5?Optimal: may turn on, detect over voltage, inform you and shut down.Bad: may turn on and show (slightly?) wrong measurementsFatal: may self destruct (a bit more likely)- far above 9.5?Well, the higher you go, the bigger the risk of self destruction.What exactly happens depends on the circuit and the amount of work (and hardware) the designer put in to handle over/under voltage cases.Anyway, a battery operated circuit should handle some supply ...

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    Full, short answer: Anything. De nada.Longer answer:- far below 8.2? Should just not turn on. (May get hot, though - very unlikely)- a bit below 8.2? Optimal: may turn on, detect under voltage, inform you and shut down.Good: may not turn on.Bad: may turn on and show (slightly?) wrong measurementsFatal: may self destruct (unlikely)- a bit above 9.5?Optimal: may turn on, detect over voltage, inform you and shut down.Bad: may turn on and show (slightly?) wrong measurementsFatal: may self destruct (a bit more likely)- far above 9.5?Well, the higher you go, the bigger the risk of self destruction.What exactly happens depends on the circuit and the amount of work (and hardware) the designer put in to handle over/under voltage cases.Anyway, a battery operated circuit should handle some supply voltage variations. Batteries' voltage drops over time anyway. So, you could try 10V with TWO diodes to drop them to around 8.6..8.8V (the drop depends on the current). If the voltage is to low, go with only one diode. Or start with 14V and use a 7809 voltage regulator.

    Good idea with the voltage regulator (like the good old 7809), just keep in mind that you have to account for the voltage drop accross them - like you have to feed in at least 12 or 14V - check data sheet.For the common ground problem - yes that is something to keep in mind. But only, if you want to measure something in your supply circuit. I.e. the voltage reglator or the solar system - and even then only, if you have to connect the minus input (aka GND) to something that is not GND. A fast triggerig fuse may help here...

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  • Turn 9V Battery to 5V Battery (simplest and cheapest way)

    No.(Well, maybe just in an emergency, for some short calls.)Take a phone battery - a common one like the iPhone 5s has a capacity of 1560mAh.Even a (very expensive - like 10US$ apiece) lithium 9V battery has only 1000mAh (the fact that it has 9V instead of just 5V doesn't matter, those 4 volts get converted to heat by the regukator...) an alkaline battery is more like 500mAh and a zinc-carbon like 250 mAh...And don't forget that the regulator has no heat sink at all. Remember those 4V voltage difference? Multiply the current needed (and a charging smart phone may want like 2A) with thos 4V to get the power this teeny tiny regulator has to convert to heat. Any more than 200mW (or 50mA) - I'm just guessing here as the data sheet says nothing about the IC in mid air - will probably fry the...

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    No.(Well, maybe just in an emergency, for some short calls.)Take a phone battery - a common one like the iPhone 5s has a capacity of 1560mAh.Even a (very expensive - like 10US$ apiece) lithium 9V battery has only 1000mAh (the fact that it has 9V instead of just 5V doesn't matter, those 4 volts get converted to heat by the regukator...) an alkaline battery is more like 500mAh and a zinc-carbon like 250 mAh...And don't forget that the regulator has no heat sink at all. Remember those 4V voltage difference? Multiply the current needed (and a charging smart phone may want like 2A) with thos 4V to get the power this teeny tiny regulator has to convert to heat. Any more than 200mW (or 50mA) - I'm just guessing here as the data sheet says nothing about the IC in mid air - will probably fry the chip.This circuit may be okay for small loads - a few 10s mA - but keep in mids that the data sheet states a minimal load of 10mA for a stable regulation...

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  • verence commented on 7q2's instructable How to Tie Your Shoelaces2 years ago
    How to Tie Your Shoelaces

    Or do it like this guy.

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  • verence commented on Hafsah Aamer's instructable The Diameter Puzzle2 years ago
    The Diameter Puzzle

    Why so difficult? Fold the circle in half - done. Doesn't even need a pencil ;-)

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  • How to Find Smallest and Largest Number in Array

    What are your tmp variables for? The are not used anyhow.Start your loop with the second element. The first one is already in small and large.for (int i = 1; i < arr.Length; i++)Why a second loop through all of the array to count the appearances of the smallest value? Do it in the first loop.if (small > arr[i]) { indexAmountSmallestNumber = 1; small = arr[i];}else if (small == arr[i] indexAmountSmallestNumber++;In that case, you'll have to initialize the indexAmountSmallestNumber to 1.Getting arr[i] four or more times can be costly. Get it once into a temporary variable and use that, or use a foreach loop.Remove your comments. They are less than helpful. For example://large == 4, arr[i] == 5Well, maybe the one time you checked it in the debugger. But will that help you to unde...

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    What are your tmp variables for? The are not used anyhow.Start your loop with the second element. The first one is already in small and large.for (int i = 1; i < arr.Length; i++)Why a second loop through all of the array to count the appearances of the smallest value? Do it in the first loop.if (small > arr[i]) { indexAmountSmallestNumber = 1; small = arr[i];}else if (small == arr[i] indexAmountSmallestNumber++;In that case, you'll have to initialize the indexAmountSmallestNumber to 1.Getting arr[i] four or more times can be costly. Get it once into a temporary variable and use that, or use a foreach loop.Remove your comments. They are less than helpful. For example://large == 4, arr[i] == 5Well, maybe the one time you checked it in the debugger. But will that help you to understand the code in two years? Good comments do not say, what the code does - good readable code does this itself. Good comments tell you why it does it this way.

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