How does the I/O fit in?

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Pish
 
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Joined: Sun Jul 29, 2012 8:54 am

How does the I/O fit in?

Post by Pish »

I'm building the VCO.

Built a little kit from maplin as the power supply.
http://www.vellemanusa.com/products/vie ... &id=350481

Put a battery on it. Connected up.
Power supply on.
TM4/5 Centred.
Checked the DC bias using my meter. CORRECT.

It performs like it should like it says in the instructions, I can hear buzzing that changes pitch
But using the sound card scope and the suggested soldered clips it doesnt look very saw like.

Anything I should check or carry on?

Image
Last edited by Pish on Wed Jul 17, 2013 6:02 pm, edited 2 times in total.

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antto
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by antto »

i'd say ignore this, either the scope or soundcard is acting weird
the VCO is biased so it might be clipping in your soundcard inputs

you could try running the probe signal thru a 1Meg pot and adjust it while looking at the scope

Pish
 
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Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Image

Image

Using 7805 tab for both power and scope grounds

Pish
 
Posts: 85
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Instead of the 10k pot on the probes?

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mmm
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by mmm »

The scope pics don't even look remotely like the real waveform.

First of all the waveform looks like it has both positive and negative symmetrical components; this shouldn't happen with the sawtooth at all.
In addition it appears as if it has just about 200mV peak to peak; this would be way too small.

I don't know if this is the result of the soundcard scope acting up.

Pish
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Any suggestions then?

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antto
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by antto »

if it sounds fine - my suggestion is to continue forward with the build
you can check the signal again once you put the VCF together

Pish
 
Posts: 85
Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Is there anything I can test my soundcard scope against?

Pish
 
Posts: 85
Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Is it worth making a little frequency generator kit to test it on?

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antto
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by antto »

well, it's up to you
but IMO you can simply continue and checks things again when you build the VCF section

Pish
 
Posts: 85
Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Cheers mate.

Ill just make sure I keep logs as i go

Pish
 
Posts: 85
Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Got a second hand, hand held Velleman HPS140. I'll give it a go tomorrow.

Pish
 
Posts: 85
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

Alot more like it!

Image

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mmm
 
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Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by mmm »

Definitely!

Let us know how everything else turns out.

Pish
 
Posts: 85
Joined: Sun Jul 29, 2012 8:54 am

Re: Testing VCO with soundcard scope. Doesnt look the same.

Post by Pish »

I was worrying I'd done something wrong but, Ive got the solder bug at the moment so I thought £40 for a £100 scope aint too bad.

Image

Built the VCF but broke the point off the probe D: !!!! Have to find/order one

Image

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