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  1. R

    Pic interface with sensor

    Hi i need to clamp a capacitor to 0.65V and then apply a pulse, then dischsrge the cap. To get a 0.65V pulse output. Thanks.
  2. R

    Pic interface with sensor

    Hi This is the curcuit i intend to use. But have the FET source connected to a 0.65V supply. Can you see issues? I need to get the pulse width correct, which i presume can be done via programming timers of the PIC.
  3. R

    Pic interface with sensor

    Ok i will upload a schematic today. Thanks for your help.
  4. R

    Pic interface with sensor

    Hi Thanks. I was not sure that i could drive the 5 sensors all at the same time. I have looked in the datasheet but cant seem to find where it mentions this. I am using a dc-dc converter to drop the voltage to 0.65V DC. Then using a p mosfet high side switch. The gate is pulsed via the PIC...
  5. R

    Pic interface with sensor

    Sorry for the confusion. Each sensor needs to be pulsed with 0.65V DC at time duration of 0.1ms (this is VHeater voltage). Then the supply VC is applied. After which the voltage out of the sensor is read back into an A/D channel of the PIC. This sequence is applied to each of the 5 sensors in...
  6. R

    Pic interface with sensor

    I will do a block diagram. It is a gas sensor. Drive is a pulse of 0.65V DC for 0.1ms. Then apply power and then read into A/D converter. The pulse circuit is driven from PIC to gate a pmos FET, which is connected to 0.65V generated from a dcdc converter. I need to drive 5 sensors, but the...
  7. R

    Pic interface with sensor

    I am using a PIC that has enough A/D channels but do not want to repeat the drive circuitry 5 times. Need to keep this common as i am restricted with PCB space.
  8. R

    Pic interface with sensor

    Hi all, I have a common set of electronics, basically a PIC and drive circuitry (pulse drive) to test a sensor. The output of the sensor is fed back into the PIC A/D. The project has evolved and now requires me to test 5 sensors. Obviously i do not want to repeat the drive circuitry 5 times, as...
  9. R

    Pic interface with sensor

    Thanks. Could it also be that i need a logic FET to drive from a PIC?
  10. R

    Pic interface with sensor

    Hi, I have tried doing some simulations in SIMetrix. (see attached) The PMOS switches when VGS < Vgs(threshold). For the IRF9530, it begins to turn on at -2V. So Q3 is off since, Vgs = 0. (Gate is 5V, and Source is 5V). When the transistor Q2 is switched on (with a pulse), we get -5V- source at...
  11. R

    Pic interface with sensor

    I will look at the p channel device you just mentioned too and do some simulations.
  12. R

    Pic interface with sensor

    It is a team of 3. One hardware, firmware and mechanical. I am doing hardware. The PIC interface is ok. Analogue electronics is a bit weak :( Hence asking for some help. I will do some simulations in Simetrix on the pulse generation tomorrow. I will let you know how i get on.
  13. R

    Pic interface with sensor

    Is there anyway I can charge a capacitor through a diode (diode giving a voltage drop of 0.6 to 0.7V). Then discharge via a pulse operated from a MOSFET? I do not know how to design this. Can anyone help?
  14. R

    4 x 7 segment common anode

    Thankyou.
  15. R

    Pic interface with sensor

    No you are correct. However, the idea with an adjustable supply and FET is incorrect. Is there a better method?
  16. R

    Pic interface with sensor

    Sorry, PGC is post graduate certificate. I want to be able to measure natural gas. Not sure about ppm levels. Need to do some more reading. My main concern at the moment is how to generate the 0.65Vdc pulse for 0.1ms. Could i achieve this by generating a 0.65V dc supply via a adjustable...
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    Pic interface with sensor

    The project is part of my PGC project. I am trying to design a gas alarm. I only chose this device because a friend of mine has a gas alarm, which he kindly took apart and let me look inside. I wont mention which company it is though. It uses a PIC and a DC-DC converter (I presume in buck mode)...
  18. R

    Pic interface with sensor

    I am waiting for information from Nissha FIS at the moment too.
  19. R

    Pic interface with sensor

  20. R

    Pic interface with sensor

    Sorry, i tried uploading a schematic but it gets to about 95% upload and then just keeps on crashing. Is there a file size restriction before i can upload. I was trying to upload a 2.6M size file?
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