generate temp.stable 600kHz sinus generator 30V from single supply 9V

Discussion in 'Analog & Mixed-Signal Design' started by patpin, May 3, 2018.

  1. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    I like to build a sinus generator. I have a single supply of 9V DC and need 30V 600Khz to feed to a small transformator with varying couplingbetween the 2 windings. (influenced by and with the purpose of detecting the presence of a rapidly passing ferrite bar). I looked for examples on the net but I didn'found one that could make 30V without dual voltage supply and meet stringing temp. compensation conditions since it should be realised on a small PCB (5x5 cm) and for an environment where temp. can reach 90°C.
    I guess the easiest would be to make a DC-DC converter functioning on that freq, so that I can tap the 600khz before the final rectifier. In fact a DC-AC converter...? Or are there better ways?
    Are there IC that I can use in order to realise (at least parts of) that?
     
    Last edited: May 3, 2018
  2. Hymie

    Active Member

    Mar 30, 2018
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    Well, you could use the 9V to supply a dc-dc converter giving a dual rail output – and then use the circuit you have found on the net.
     
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  3. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    Thanks ! Whats the most compact way to make a 600kHz DC-AC converter, that can be used in temp's of 90°C. Are there specialised IC's and do I need always a trafo?
     
    Last edited: May 4, 2018
  4. Sensacell

    Moderator

    Jun 19, 2012
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    Maybe we could be more helpful to you in solving the first problem- detecting the ferrite bar?

    Can you tell us more about that?
     
  5. DECELL

    Member

    Apr 23, 2018
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    I think its very likely you are making an LVDT type device. If that 's the case, can you live with a lower sensitivity, maybe 20%. then a lower exitation voltage (Say 6v?) will work fine.

    [​IMG]
     
  6. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    The ferrite bars are part of a rotor which can turn 6000RPM and has 12 small (1cm long x 2mm diam) ferrite bars each 30°. There is a transformer nearby (.5mm) and the core consist of ferrite but is open, probably E shaped. On one winding the 600Khz 30V signal is always present. On the other the signal is detected. When the ferrite comes near the transfo, the amplitude rises to 3.5V. When not it is below 1.5V. This signal is then interpreted further on. My objective is to produce the 30V 600khz signal. The currents are probably in the order of 1mA. The gauge of the windings is about 0.2mm for the 'sender', less for the 'detection' windings; don't know number of winding.
     
  7. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    The motion is not lineair or rotatory but rather tangential. But indeed there is much rassemblence and maybe the excitation/detection circuits can be very usefull ! You have realised some and with what kind of IC's? The pickup module I have has only two L's.
    I have to mention that besides the high temperature problem there is also the presence of high voltage at a distance of 5cm ( up to 40KV and pulsed 1mSec duration every 1.6mSec).
     
    Last edited: May 4, 2018
  8. crutschow

    Expert

    Mar 14, 2008
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    Is that 30Vrms, 30Vpp, or 30Vpk?
     
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  9. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    I guess a DVM measures Vrms, so this is what I need since specifs on manual (of old defectuous circuit) tell to check for 600kHz 25 to 35V..Once I remember having seen 29Vpp on scope. In the case of 30V rms as in specifs, I should have seen a Vpp of 84V which I never saw, and still... every thing functioned well at that time...
     
    Last edited: May 4, 2018
  10. dendad

    Well-Known Member

    Feb 20, 2016
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  11. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    Thanks for info. I had been looking for the PGA970 but it's way to expencif. Also the AD598 125°C version is at 99€. A bit to much for experimenting with it. Indeed, I thougt making the excitation part and then later design the demodulator and low pass filter and comparator opamp to detect when ferrite is moving away form the mini trafo constituting the pickup module.
     
    Last edited: May 5, 2018
  12. DECELL

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    Apr 23, 2018
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  13. DECELL

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    Apr 23, 2018
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  14. patpin

    Thread Starter Active Member

    Sep 15, 2012
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  15. patpin

    Thread Starter Active Member

    Sep 15, 2012
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    Since I didn't receive an anwer, I designed another sine generator which appears to function well. my question is how can I model the influence of long wires (.75 meter) to the pickup module L3.
     
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