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  1. P

    555 timer circuit

    Connect a 1nF capacitor between IC1 pin 3 and IC2 pin2. As the night sensor activates and takes pin 3 low, the cap will produce a negative pulse at pin 2 to trigger the timer. After the pulse has ended pin 2 will go high and the timer will work normally.
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    Help with Gain

    When I was studying electronics almost 50years ago, I was censured by my tutor for not realizing that the result of the formula dB = 20 log10 (VOUT / VIN) could only be correct if the two voltages were measured across a common impedance. This is also implied in the second para of the section...
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    Help with Gain

    The decibel is a measure of power ratios, so you will need to know the input and output impedances.
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    DC-DC buck/boost converter

    Thanks Harald, I contacted the Chinese supplier and got the sort of reply I expected, which was - "sorry,i cant understand the problem". I feel sure your first suggestion will prove to be correct. Happy new year, Peter
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    DC-DC buck/boost converter

    I was going to but then thought I would probably get an incoherent answer. Still, I'll give it a try.
  6. P

    DC-DC buck/boost converter

    Can anyone explain the purpose of the centre one of the three pots in this converter? The spec seems quite vague about it...
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    Arghhh! I Hate RS232 :)

    I assumed this was for a one-off; I didn't know you were going into production with it. In that case it would be better to stay with the RS232, because hacking into a large quantity of boards to get to their CPUs is not a good idea.
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    Arghhh! I Hate RS232 :)

    @Ernest My understanding of the bits of the three quotes I have underlined was that: 1. You had a WiFi where you could access raw data 2. You wanted to transport its data to 3. A proprietary board that fed into a CPU whose ports you had access to. That being so, my idea was that because...
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    Arghhh! I Hate RS232 :)

    "That fella" was only offering help, bearing in mind that you said "I also want to get as far away from virtual COM ports as possible. It's so 1970's". The solution I offered was definitely "not 1970s" and would have meant just a single IC at each end for one-way communication; or plus three...
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    Arghhh! I Hate RS232 :)

    That's an illogical question. Why did you ask it?
  11. P

    Arghhh! I Hate RS232 :)

    I read it several times. I also saw from post #12 para2, that the OP had already bypassed the RS232 link and gone straight to the CPU. On that basis he could dispense with the RS232.
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    Arghhh! I Hate RS232 :)

    (quote)That's an RS-485 transceiver, not RS-232. But thanks for playing!/quote) The OP said he wanted to input 3.3V TTL into a some form of converter at one end of the cable and get Tx, Rx, and GND out of a converter at the other end. So I had assumed that he didn't mind what protocol was used...
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    Arghhh! I Hate RS232 :)

    Another chip that may fill the bill is the SP3485. If you look it up on the RS site and it will point you the data sheet for it.
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    Koford (Slot Car) Bench Power Supply Project

    @Chad If the glue can be squeezed out of the glue gun, it is hot enough. Did you leave it long enough to harden properly? Were you using the ‘bathroom sealant’ type of silicon rubber? Again, it needs time to cure. @Steve Chad said he wanted to hold a large electrolytic and a rectifier in...
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    Koford (Slot Car) Bench Power Supply Project

    I use a hot glue gun for that sort of application - it's fairly quick drying. An alternative might be silicone bathroom sealer, but there is a faint smell of acetic acid when it is curing and I'm not sure whether the fumes would affect the components.
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    remote sleep

    The MSP430 is a micro-controller . A PIC or Arduino would also do the job of decoding the audio signal and switching a relay, and many members could help you. But details of the acoustical signal would need to be known in order to write a program.
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    remote sleep

    Got it. So the amp IS the current source and you want a means to turn it on and off remotely. You say: "What I need to do is figure out a way to receive a pulse (the signal sending side is done) and power the amp on/off". How are you going to send the signal to the amp - through hardwiring or...
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    remote sleep

    We may be talking at cross purposes. I assumed you had a 4-20mA current loop going to the input of a remote instrument amplifier. I was asking what the input resistance of the amplifier was, ie. what load the loop would 'see', and what would be the open-circuit voltage of the current source if...
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    remote sleep

    5V seems too low, 'cos 20mA through 350ohms is 7V.
  20. P

    remote sleep

    Do you know the open-circuit voltage of the 4-20mA loop? And the terminal resistance of the loop in the device?
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