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  1. Merlin3189

    With sending one pulse into a motor, does that make it move a step?

    As far as I can see, there are only two basic types of motor where the question would be relevant; stepper motors (most likely), which are designed to be pulse driven , or DC motors which are designed to be run on a constant DC, but could be driven by a suitable pulsed supply. The whole point...
  2. Merlin3189

    Help With an Equation

    How about using ratios?: 0.1/5 = 1/50 (making both numbers 10x bigger keeps the ratio the same) So RDS / (RDS + RL) = 1 / 50 So whatever RDS is; 1 Ohm, 1 kOhm, 1 lot of 270 Ohm, etc. then (RDS + RL) is 50 of them; 50 Ohm, 50 kOhm, 50 lots of 270 Ohm (ie. 13.5kOhm), etc. The RDS is one of...
  3. Merlin3189

    Anyone Else Read This?

    But when I looked at her info on the Google site https://www.googlesciencefair.com/en/projects/ahJzfnNjaWVuY2VmYWlyLTIwMTJyRAsSC1Byb2plY3RTaXRlIjNhaEp6Zm5OamFXVnVZMlZtWVdseUxUSXdNVEp5RUFzU0IxQnliMnBsWTNRWXA2ZVVBZ3cM she has done this in her research
  4. Merlin3189

    Circuit Diagrams

    I'm intrigued! So what is top and why? Or do you just mean that, now we know the Earth is spheroidal and a sphere does not have a top? (Though if a billiard ball is on a table one might reasonably say the point in contact with the table is the bottom and the opposite point is the top.) My own...
  5. Merlin3189

    What is the difference between volt per second and volt-second?

    At the risk of unnecessarily confusing the situation, is not quite right. If velocity = Voltage, then Volts/Seconds = velocity/seconds = Acceleration, and Volt*seconds =velocity*seconds = distance. The interesting thing about this question is, where would this question specifically arise? In...
  6. Merlin3189

    Anyone Else Read This?

    My first reaction to Cdrive's original post was, is this possible? So I did some sums and in looking up data, I found this http://www.customthermoelectric.com/powergen.html?gclid=CIat-pKS570CFZShtAodqm0AfQ Where I'm a bit stuck at the moment, is in estimating the amount of heat your hand can...
  7. Merlin3189

    Voltage conditioning circuit

    What I think you need is an anti-log or exponential amplifier, which uses the.exponential relationship between current and Voltage of a diode. A brief description of the principle is in Wikipedia, but I don't know where there is a description of a working circuit. Google may help.
  8. Merlin3189

    Voltage Regulator Heatsink

    What you need is the thermal resistance. You've done the hard part and found a decent data sheet, so you know this is 19 deg C per Watt. That means for every Watt of heat generated by the device, it's temperature will rise by 19 deg C above the surrounding air when mounted on this heatsink...
  9. Merlin3189

    Wafer Vibrations

    Vibrations in a speaker If I understand you right, you want to power a speaker from an AC source and rheostsat. Certainly you can do this, though 120V seems far too high to be sensible and you will get vibrations only at 50 Hz (or 60Hz depending where you are.) You'd be better off finding a...
  10. Merlin3189

    Wine heater

    Thanks Harald. I had not spotted that.
  11. Merlin3189

    Schmitt trigger relaxation oscillator

    The standard transistor Schmidt trigger thresholds are set by combinations of resistors to be a fraction of the supply Voltage, but not necessarily .33 and .66 By choice of the resistor values both thresholds can be set and a variable resistor may be used to adjust them in use. Because the...
  12. Merlin3189

    Power Supply

    But notice it is 12V AC output, whereas your original is 12V DC. So you would need to add rectification. Depending on your application you may need to add smoothing and regulation to both. Your first one has got a rectifier and probably a capacitor, but often that's all. I'm a great fan of...
  13. Merlin3189

    Need help with voltage divider circuit calculations

    Fair point BobK.
  14. Merlin3189

    Wine heater

    In some ways I prefer this circuit to your 741 circuit, but I still wonder about the negative temperature coefficient thermistor. If I am right about it, then you just need to swap the thermistor with the adjustable resistor, so that it switches off as it warms up. The other point in both...
  15. Merlin3189

    Need help with voltage divider circuit calculations

    One general tip about rearranging formulae: Put in all the numbers you know first, before you rearrange the formula. Firstly, some numbers may simplify, so you have fewer things to juggle. Secondly, most people can rearrange numbers a lot better than symbols.
  16. Merlin3189

    Relay Problem

    May I just ask, what the relay is switching on? As I see it, the thermistor has a negative temperature coefft. So when it gets warmer, the resistance gets lower and the Voltage at the - input goes lower making the output go high and switch on the relay. So a higher temperature switches on the...
  17. Merlin3189

    Worldwide lighting made 20% more efficient

    Would it not be more accurate to say, "ALL consumers pay for the increasingly poor PFC of many users, but most are not rewarded for improving their own."
  18. Merlin3189

    Schmitt trigger

    = Right. I'd have guessed nearer +13V, but you are drawing 40mA, so a lower Voltage might be expected. = But the question was, at what value of Vin? So see below. = as said before, it is positive feedback, otherwise good. OK, in a) what is the Voltage on the + input? It is +9.41 *...
  19. Merlin3189

    Over-voltage & over-current Protection

    Maybe R1=R2 and the base of Qm and the inverting input of op amp should be connected to this point. Then the op amp is comparing 6V with half the output: so output =12V. Rs is a current sense for short circuit of the output, developing a Voltage across the base-emitter of Qm. If the current...
  20. Merlin3189

    DC Shunt Motor

    Because there is a current in the field winding producing a magnetic field. A coil rotating a a magnetic field generates an emf. At the ideal free-running speed this will exactly equal the applied Voltage, so no current flows. Though, as has been said, this never really happens, so there...
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