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  1. M

    Highside mosfet gate spike

    Hi guys. A while back I ask for, and received, a whole lot of help in regards to creating a motor controller. Happily it all worked out well in the end. I have recently decided to redesign the controller. Now I'm using pSpice to cut down on blowing up components. The circuit I have uses an...
  2. M

    SG3524 question

    One simple question about the SG3524 regulating PWM chip. The error amp inputs are pins 1 and 2, the output of the error amp (and the compensation) pin is pin 3. The current limit amp inputs are 4 and 5. The current limit amp will over ride the output of the error amp. My question is, if I...
  3. M

    Current limit delay

    Hi guys, I have a motor controller that uses the SG3524 chip to generate a PWM pulse. This is sent to mosfet drivers which run an H bridge setup. The onbard current limiting is resulting in a "jerkiness" of the motor when it starts to hit the 0.2v limit on the CL + pin of the SG3524. The...
  4. M

    4PDT to SPDT trick

    Hi guys. I have a circuit that uses a 4PDT switch to flick 4 seperate parts from one circuit to another (if that makes sense). Is there a way to use a SPDT switch in conjuction with some electronic switches to do the same thing? I thought I could use the MAX333CPP quad SPDT analogue switch...
  5. M

    Negative Voltage Rail Sag

    Hi guys, This is part of a motor controller circuit. It is designed to function as an inhibitor from switching directions if the motor is still moving. It works MOSTLY as intended, ie if the motor is spinning forwards (even with no speed demand) and then is flicked into reverse, the circuit...
  6. M

    Latching comparator help

    Hi guys, I have built the following circuit. The Vref is 0.01v. The Vin ranges from 0 to maybe 5v at most. What I was intending was a comparator that latched on once the Vin was less than Vref (and in which case the LED would illuminate). The trouble I have is that when it turns on, the...
  7. M

    Switching idea

    Hey everyone, I would like to design a setup that switches a PNP transistor on when a signal reaches near 0v (it would normally be either +ve or -ve), and then keeps that transistor on until the system is reset. My current thoughts on the matter are to have a window comparator to detect the...
  8. M

    Mosfet driver not outputing properly

    Hi guys. I have constructed this circuit. Everything seems to work as expected, except for one small problem. The high output of both the IR2184 drivers is not high enough. I ran into this problem with an earlier circuit (also posted) and was helped to solve it by decoupling the driver...
  9. M

    Glaringly obvious errors

    Hi guys. Could someone please have a quick look at the circuit below and let me know if there are any glaring obvious errors that would result in smoke and/or flames when a battery is connected to it. Many thanks
  10. M

    Switching circuit

    Hi guys, Is there anyone out there that knows of a switch that can be turned off electronically, but needs to be manually switched back on?
  11. M

    Transistor clarification

    Could someone please clarify what emitter-base voltage is on a transistor for me. Could I, for example, have a transistor with a Veb of 6v with the base of the transistor connected to a 12v source (assuming the collector-emitter side was also connected to the same 12v source)? What about the...
  12. M

    Regen braking question.

    Pretty straight forward question..... If a motor is set up to regeneratively brake, and it is being forced to turn, would that put a negative voltage across a sense resistor on the low side of the H bridge? If not, is there a way to measure the current being produced by regenerative braking?
  13. M

    Half bridge driver

    I have built this circuit but it does not appear to work as i expected. I assumed that it would drive a motor quite happily at what ever speed was selected via the variable duty cycle PWM input. If a low duty cycle was selected and the motor needed to slow down the inverse pulse going to the...
  14. M

    Comparator help

    This is my current circuit as it stands What I am trying to get is the LED to turn on when the voltage across the sense resistor (0.32 ohm) gets above 0.2v I have set up the LM311 comparator as shown. However it doesnt seem to work as I thought it would. The LED turns on as soon as there is...
  15. M

    Current Limiting Indication

    Hi guys. I have made this circuit, and it works well. You can vary the duty cycle between 0 and 90% and the current limiting kicks in as the voltage on the C.L (+) sense (Pin 4) starts going above 0.2v. However I would like some sort of indication as to when the circuit starts current...
  16. M

    IC output help

    Hi guys. I have made a circuit that uses a UC3843 in order to run a 12v lamp and be able to dim the lamp. I can get an the voltage on PIN 1 of the chip (the ouput of its error amplifier) to vary between 0.8 and 7.26 volts (which I believe should be enough to vary the output duty cycle between 0...
  17. M

    Variable PWM with chip

    Could someone let me know if the following setup on the UC3843 chip is actually going to produce a user variable PWM pulse to the MOSFET driver chip? Specifically, if the variable resistor doesnt work like this, how could I set it up? Thanks
  18. M

    UC3843 for a motor controller?

    I am tossing around a few ideas as to making a motor controller for an electric wheel chair type thing (it'll need to handle a fair current from a 24v motor). I was thinking that pehaps the UC3843 would be a good PWM generator for this. My reasons for thinking this (which may be incorrect) are...
  19. M

    Soft start on a 555 timer

    Can a soft-start being implemented on a 555 timer through the control voltage pin (number 5). What I am after is to start the 555 up at a low frequency and have it ramp up to a higher frequency slowly. This is what I have in mind so far My question is  - will this circuit addition mean that...
  20. M

    Coil gun charger circuit

    Hi guys. I have come up with a schematic for a coil gun capacitor charger circuit. It should run off a car battery (12v). It is currently set up to charge up a 50v capacitor but I designed it to go up to close to 500v (the max rating for the diode), by just changing R4. What do you think?
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