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  1. dorke

    Vintage Heathkit 4001 weather station how to split sensors between two consoles

    Bob, What would be the distance between the consoles?
  2. dorke

    Single phase to three phase motor

    Very simple, you can't !
  3. dorke

    Exactly how evil are Capacitors?

    Disagree! Low voltage can't electrify a person but, in some cases the current can cause very serious injures. Have you ever seen a thin wire short out a car battery(which is actually a capacitor charged to "only" 12V)? The current will melt the insulation and burn the wire. If there is a person...
  4. dorke

    clever I2C/SPI switch: fail

    GPG, Nice part, but rather expansive for that app.
  5. dorke

    BJT current gain

    OrangeArav, Put aside your calculations and try to think about the all thing as composed of cascaded basic building blocks! The last stage is a C.B amplifier Q3 with RC=R10 . for that you already have the Av,Rin,Rout formulas "ready made"(you can develop that if you want,but absolutely don't...
  6. dorke

    Is this device a thermistor?

    What are points P1, P2(DC volts) ? What kind of relay is U1(DC?) Can you please re-check the diagram connections for possible drawing errors? As for the diodes ,like that:
  7. dorke

    Is this device a thermistor?

    I find the diodes U4-U7 connection vary strange. Are you sure about it?
  8. dorke

    Soldering station SMD+THT: Hakko or Chinese?!?

    I use this hot air and very pleased with it. I have a Weller WECP-20 soldering station ,if you can get one(used?) it will serve you good. But, you can buy a cheap Chinese one,the important thing is good quality tips and shapes. If it suites you better you can get a Chinese combo .
  9. dorke

    Soldering station SMD+THT: Hakko or Chinese?!?

    The first question to ask is : Do you intend the equipment for "professional use", repair or hobby projects ? That is determent by the "usage time" and quality of work needed. If it is for "pro" go for the best quality equipment in your budget . for hobby go for the china stuff. I myself,use...
  10. dorke

    BJT current gain

    I think it would be easier to split the all thing into 3 stages which are cascaded. There is a requirement to use voltage dividers. For each separate block calculate Av,Rin,Rout while assuming it is driven by a voltage source . Now, Vout= Vin*[Rin1/(R2+Rin1)]*Av1 *[Rin2/(Rout1+Rin2)]*Av2...
  11. dorke

    What is a 'High/Low Level Trigger'?

    Paul, your welcome. There is one issue though. The PIR is intended to identify movement of humans,will it work with woodpeckers(much smaller)? If at all,at what distance?
  12. dorke

    What is a 'High/Low Level Trigger'?

    Yes exactly.:)
  13. dorke

    What is a 'High/Low Level Trigger'?

    Here you have the user manual of the ISD18B20 The voltage to the player is VCC=2.4-5.5VDC you don't need to switch it. You need to use(switch) PlayL input ,Level-activated control. switching it to High(=VCC) will play, taking it back Low will stop the playback. Also, activate the "REPEAT"...
  14. dorke

    Variable capacitor

    That is not complicated at all,here is the Cap/Vr graph from the BB112 datasheet . you can see the points you need (typical value). Since Vr/Cap is a logarithmic relation in Vr, it is better to use a logarithmic pot. to obtain the Vr needed. You can usea 1K ohm pot and 1M,resulting in a higher...
  15. dorke

    Variable capacitor

    The BB639 diode will not work in your circuit: 1.It needs much higher "tuning voltage" up to 28V 2.in the range 1-9V(that you have) you will get about 10-40pF while you need 85-365pF Use the BB112 ,you can get here . The 100k pot is o.k,but better use a log one not linear to give you more "hand...
  16. dorke

    Questions about UART communication

    Max, It was clear from the beginning you connecedt 2 μC (most likely on 2 different boards) with Uarts, in a very short distance (same table?). As I said above (#2 reply), you need to connect the grounds of the 2 boards for it to work (and preferably run at the same voltage value). In...
  17. dorke

    Questions about UART communication

    1.The receiving end gets the voltage between the wire and it's own ground, if both grounds are not related the voltage "seen" by the receiver is obviously not correct. to fix that you need to run 2 wires(signal+gnd),that will only work for very short distances. 2. Yes,the FSK receiver will...
  18. dorke

    Remote switch

    The simplest solution would be to locate the source that is driving the speakers(probably some kind of audio PA of a public address system). Assuming the PA is located in a place near the operator it need not be with remote control. A simple mains rocker-switch(DPDT) would do the job: switch...
  19. dorke

    Help Removing Bulbs from Mini Christmas String

    Alen, There are so many options out there for LED chains many colors to chose from,safe,and very cheap. Absolutely no reason to DIY
  20. dorke

    clever vibration motor driver?

    I keep a " cemetery box" of bad/blown etc. parts. This link shows how far have we came from 1Hz corner(pole)... how amazing and wonderful;)
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