Raspberry Pi Forums

pygmy_giant

I'm happy to wait - lots of other things to play with while its being perfected...

pygmy_giant

thanks

pygmy_giant

Thanks - I will look into a colpitts oscillator. I thik the 555s used in the theraminvision circuit are high frequency cmos ones that max out at 3Mhz (not your normal NE555). I thought an op amp was a type of comparator - I know they can be turned into al sorts of logic thingies.

pygmy_giant

Something like one of those does look good - if only there was something avaiable and fully developed that could turn the Pi into an affordable oascilloscope, like on the panalyser thread.

pygmy_giant

Thanks - I see what you mean about the frequency issue with op amps - cursory googling reveals that the gain is commonly effected at high frequencies. I will see if there are high performing high frequency op amps available before abandoning this avenue - the 555 seems to have op amps inside it so p...

pygmy_giant

I don't think the theraminvision kit is still available (if it is please direct me to where I can buy one) - so if I can hit on a solution that is easier to build, then I might use it. I'm also enjoying learning about the subject (making a fool of myself in public - not so much). If I can find a sol...

pygmy_giant

It's not an oscilloscope, but I downloaded the free idealCircuit simulation software for Windows today and and am finding it easy to use. After drawing your circuit you can insert virtual probes to give osciloscope type output. I have been taking the basic parameters from device datasheets and feedi...

pygmy_giant

I have downloaded the 'idealCircuit' simulation software and come up with the following: http://www.nsd.uk.com/miscellaneous/circuitI.PNG It is basicly two oscilators with a summed output that is put through a low-pass filter. The bottom one is slightly out of tune with reference oscilator above. It...

pygmy_giant

oh - yes thanks - looks like I'm wrong and ravenous is right... :oops: I can see that C3 is connected to the input of the both op amps - perhaps the antenna could go on C2...? Need to research more - the need for all three capacitance values to be matched in order for this to work properly as a 'qua...

pygmy_giant

The quadrature oscilator is made from 2 oscilators - as far as I'm aware, these are not synced together, hence the need for C1 and C3 to be matched; I beleive C2 relates to the phase relationship, and could be omitted as I'm not bothered about that. http://www.changpuak.ch/electronics/images/Oscilla...

pygmy_giant

Nice!

If you had longer screws could you fix 2 together?

Would it be possible to have a downstairs compartment with a battery pack?

pygmy_giant

but then you also have to buy all the components and discard them when you discover that your amazing idea was based on a lie - think I'll try and hunt down some free circuit modelling software.... and then buy an oscilloscope and the parts if it looks like a goer My £1 multi-meter off of ebay works...

pygmy_giant

I disagree - the phase shift is governed by C2 (which could be dispensed with). I have seen the circuit with health warnings stating that the two parts must be tuned exactly to work properly, so de-tuning it shouldn't be a problem ...? Think this could be exactly what I want and not too complicated....

pygmy_giant

Or..... perhaps I could use a quadrature oscillator : http://www.changpuak.ch/electronics/images/Oscillators-1-4.png and de-tune the second oscilator section by connecting an antenna to c3.... (When R1xC1 = R2xC2 = R3xC3, the circuit oscillates at ω = 2πf = 1/RC.) ... and maybe then use a third op-a...

pygmy_giant

Better that end - elecric windows arent always better than the olden fashioned windy ones - the worst story I ever heard involved one of those motorcycle helmets with a ledge that clips up under the chin (visor down). Could have been worse - he could have succeeded in drink riding :mrgreen: Sines ca...

pygmy_giant

I feel sea sick

pygmy_giant

Thanks for the encouragement. The flexel thingy has lots of sockets for lots of goodies - 4 of these can take servos, so I thought maybe the antenna could move, or you could even just have one sweeping back and forth. I also thought that two independently moving adjacent antenna could perhaps angle ...

pygmy_giant

Thanks it does.

So in a nutshell - my simple solution would require an atomic clock to be usable

Will simultaneously explore hetrodyning and bodged solutions: http://www.youtube.com/watch?v=Ij8DcJnVk1c

pygmy_giant

@ravenous Ignore my waffle - think you have something there - perhaps all thats needed is a circuit like this: http://www.nsd.uk.com/miscellaneous/theramin%20sensorII.jpg - the trigger and output could be connected to the GPIO (via resistor divider for return signal). Then the Pi would just have to ...

pygmy_giant

Good point - potential banana skin there is that the Pi has not yet got a good reputation for accurate real-time measurement, although the panalyzer thread shows promise. Might try that this weekend anyway to see if it generates usable results. My reason for favouring the I2C ADC approach is that I'...

pygmy_giant

Thanks for the crystal suggestion - will explore... I'm certainly learning as I go with this... My understanding is that the fundamental priciple being exploited is the effective incorporation of the environment into the sensing circuit via the antenna due to it's capacative properties. I think the ...

pygmy_giant

:oops: think I'm going about this all wrong....! Think I should do: high frequency capacitance sensing 555 astable circuit as in theraminvision manual (generates oscilating signal) ---> monostable circuit (provides single pulse of defined width for each of the astable's oacilations) ---> lowpass fil...

pygmy_giant

As Mike says, I would be wary of connecting anything with a coil directly to the GPIO due to emf kickback after the supply is switched off. I would use a buffer using ULN2003 or similar - if you're lazy like me you can buy a steppermotor driver board off ebay for about £1.50 and use that.

pygmy_giant

another tip - put tape / epoxy over the stopper or it will, over time, shake loose and leave a puddle of ink in the borrom of your printer

pygmy_giant

This thread: http://shkspr.mobi/blog/index.php/2012/07/3g-internet-on-raspberry-pi-success/ indicates that there are also limits to the periferals that can be powered through the USB without a powered hub - annoying isn't it. Nikola Tesla looks like this: http://upload.wikimedia.org/wikipedia/common...

Search found 1562 matches

Re: Puppy Progress ?

Re: theramin

Re: theramin

Re: Which Oscilloscope?

Re: theramin

Re: theramin

Re: Which Oscilloscope?

Re: theramin

Re: theramin

Re: theramin

Re: Pibow (a colourful case for your Raspberry Pi)

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: theramin

Re: Power a chassie fan

Re: Case Design - Internal Mounting: Raspberry Sandwich!

Re: How strict is the power supply data