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?

 

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?

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.

 

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.

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?

 

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

Can you tell us more about that?

 

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.

 

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

Can you tell us more about that?

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.

 

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.

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).

 

Is that 30Vrms, 30Vpp, or 30Vpk?

 

Is that 30Vrms, 30Vpp, or 30Vpk?

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...

 

Can you retrofit to a specialized chip like an AN598? The DIP part is rated to 85C. And the DIP part could be used on a proto board.
http://www.analog.com/media/en/technical-documentation/data-sheets/AD598.pdf

There is also the PGA970 and it has a higher temp to 125C, but it is a surface mount one.
http://www.ti.com/lit/ds/symlink/pga970.pdf

Is there already part of your system in place and you just need the excitation signal?
A bit more info could be a real help.

 

Can you retrofit to a specialized chip like an AN598? The DIP part is rated to 85C. And the DIP part could be used on a proto board.
http://www.analog.com/media/en/technical-documentation/data-sheets/AD598.pdf

There is also the PGA970 and it has a higher temp to 125C, but it is a surface mount one.
http://www.ti.com/lit/ds/symlink/pga970.pdf

Is there already part of your system in place and you just need the excitation signal?
A bit more info could be a real help.

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.

 

Can you retrofit to a specialized chip like an AN598? The DIP part is rated to 85C. And the DIP part could be used on a proto board.
http://www.analog.com/media/en/technical-documentation/data-sheets/AD598.pdf

There is also the PGA970 and it has a higher temp to 125C, but it is a surface mount one.
http://www.ti.com/lit/ds/symlink/pga970.pdf

Is there already part of your system in place and you just need the excitation signal?
A bit more info could be a real help.

 

https://www.google.co.uk/url?sa=t&r...1968-Pei.pdf&usg=AOvVaw3b6z_63TuDIg2LOOlfBLsm

Rock solid sine source...

 

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwi8weK6lPbaAhWLCcAKHUDbC4AQFggqMAA&url=http://www.analog.com/media/en/technical-documentation/lt-journal-article/05_03-12-LTC1968-Pei.pdf&usg=AOvVaw3b6z_63TuDIg2LOOlfBLsm

Rock solid sine source...

Looks good. thanks.
In the mean time I tried to design one with the Hartley and opamp but I cant get it started although I added a temporary sinus gen signal, Any idea on what I missed?

 

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.