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  1. R

    Testing TVS diode

    Hi, Thanks. Is there anyway I can simulate this is PSPICE or Simetrix? Thanks in advance.
  2. R

    Testing TVS diode

    Hi I have done exactly as you suggested. 40V with a 1K resistor, the voltage across the TVS was 23.9V which is the breakdown voltage. Does the 40V have to be a fast pulse?
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    Testing TVS diode

    Yes, but I want to see the clamp voltage at 32.4V working. How can I test for this?
  4. R

    Testing TVS diode

    Thanks for the help. I am still not sure how I can test the clamping effect? My understanding was that a voltage spike >32.4V would clamp the output. I am not sure how It can do this.
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    Testing TVS diode

    Hi, this is what I can't see, I had the voltage set to 30V, with a 1K series resistor. The voltage across the TVS was 22.8V, should I reduce the resistor value. Also how can I get this to clamp? The datasheet says VC @ IPP max, which is 15.7A. I was thinking of 34V with a 10R 10 W resistor. So...
  6. R

    Testing TVS diode

    Hi, Thanks for the information. I am trying to work out the VBR, of the device I have selected. It has a VBR of 22V. I have increased the voltage on the device to 24V, with a series limit resistor. Should I not see an increase in the current?
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    Testing TVS diode

    Hi, I had a look but there is no test circuit that I can try out.
  8. R

    Testing TVS diode

    Hi,thanks. I saw that regarding the breakdown voltage VBR. How will I test the clamping voltage?
  9. R

    Testing TVS diode

    Hi all, I have selected a SA20A to try out and test for my own understanding. I am thinking of the following: 1. Measure VBR by placing resistor in series say 10K at 10V so we get 1mA. Would this give me the break down voltage. 2. The reverse voltage, should not affect any operation of a...
  10. R

    Relay help (opto mos)

    Hi all, Is the placement of the diode in my schematic correct? Or should it go across the output pins of the relay? Thanks in advance
  11. R

    Relay help (opto mos)

    Thanks.
  12. R

    Relay help (opto mos)

    Not sure but it may because of the noisy voltage from the car battery. Also does the position of the diode look correct?
  13. R

    Relay help (opto mos)

    The current of the LED Led current is 900uA Load is 7805 + opamp circuit configured as non inverting amplifier. I do not think it is inductive, the current through the load is not substantial, about 50-100mA. Hence I think it is a voltage spike issue.
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    Relay help (opto mos)

    It fails open circuit. it's a photo relay, MOSFET type. The load is power to a couple of circuits, one is a voltage regulator 7805, then this is used to power a opamp (non-inverting), single sided to 5V.
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    Relay help (opto mos)

    Hi all, I have attached a schematic of an issue. I have a relay AQY212S, which is fed from a car supply of 12V. This is then switched by a relay. The relay is breaking down, I think it is due to voltage. The relay is rated at max load voltage of 60V. I am thinking of using a diode suppression...
  16. R

    Spi connections

    Hi, I did some research and it said what I have mentioned on one website, but on another it was different, hence I wanted some clarification. That's all. Sorry.
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    Spi connections

    Hi all, I am connecting a 4 wire spi to 4 wire spi. Master is a micro, slave is a temp sensor. Do I connect as follows SCLK to SCK SS to CS MOSI to MOSI MISO to MISO The micro is the master. Thanks in advance
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    Why a pull down resistor for transistor base

    Yes you are correct. I measured the current going from the 5V rail when the relay and green led are on, it was 72mA. The current through T1 is 5V/10K = 0.5mA. So when I calculated the base resistor value for T1 I added 72mA + 0.5mA / 200 (min Hfe). Was that incorrect? Thanks in advance
  19. R

    Why a pull down resistor for transistor base

    Hi,the 72mA is current through the LED and Relay together. Yes it should be 5V/10K. Ok, hopefully the microcontroller will only operate it's GPIO at 3V high and OV low. If the low is <O.8V and I will not get the problem.
  20. R

    Why a pull down resistor for transistor base

    Hi I have calculated the following: Current through T2 and Green LED is 72mA Base current for T2 = 72mA/120 = 600uA Base resistor for R4 = T1 VCE 5V - VBE T2 0.7V 4.3/600uA = 7.1K They have this as a 1K. T1 Ic = 72mA + (5/10K)= 72.5mA T1 base current is 72.5mA/200=0.362mA T1 base resistor...
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