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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Baby 8 Issue
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sharkattackeddie



Joined: May 24, 2016
Posts: 6
Location: UK

PostPosted: Tue May 24, 2016 5:01 pm    Post subject: Baby 8 Issue
Subject description: A problem with my Baby 8
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I've breadboarded up a baby 8 (it has four steps at the moment as that's all I can fit). It seems to work ok, except that the output is 0v for most of the wipe of the 100k lin pots I've used. I'm running it on a 9v supply and using 1n914 diodes (1n4148s didn't make any difference either).
Anyone have any idea what the problem might be?

As a side note, which value should I change in my 555 astable I'm using as the clock to allow it to output a higher frequency? I have a 1m pot in there at the moment.

Cheers!
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Steveg



Joined: Apr 23, 2015
Posts: 182
Location: Perth, Australia

PostPosted: Wed May 25, 2016 1:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Sharkattackeddie, Best sight-unseen guess is the output is being loaded down too much. Which schematic are you building from? What supply voltage are you using? What type of LED's are you using? Have you double checked the resistor values to the LEDs?
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sharkattackeddie



Joined: May 24, 2016
Posts: 6
Location: UK

PostPosted: Wed May 25, 2016 4:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Steve, thanks for the reply. I've based it on this diagram: http://electro-music.com/forum/phpbb-files/baby_sequencer_v1_128.jpg

It's running on a 9v supply (too low?). The LEDs are 3mm rose coloured, water clear from TruOpto. I've checked the resistor values and they're correct: 10k. Removing the LEDs does seem to increase the range of the voltage slightly but there's still quite a significant dead spot coming from the pots.

Is there anything else I can do to make diagnosis easier? Measure voltages at certain points, say?
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Steveg



Joined: Apr 23, 2015
Posts: 182
Location: Perth, Australia

PostPosted: Wed May 25, 2016 5:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi. There are a lot of circuits out there but that one seems to have a good track record of successful builds. I looked up those LEDs and they have a quite large voltage drop - 3.1 V typical which should help. Some actual voltage measurements could certainly help. Also check that the common negative terminal of the pots is actually connected to battery negative. The circuit will sort of still work if it isn't by making a circuit back through the other 4017 pins. Cheers!
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Wed May 25, 2016 5:53 am    Post subject: Re: Baby 8 Issue
Subject description: A problem with my Baby 8
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sharkattackeddie wrote:
As a side note, which value should I change in my 555 astable I'm using as the clock to allow it to output a higher frequency? I have a 1m pot in there at the moment.

Use a smaller timing capacitor, the one between pin 2 and GND of he 555 (1uF at the moment)

as for the circuit not functioning properly, if the LEDs are sequencing than it most be either something with the pots or the diodes.

oh and
welcome party!

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piedwagtail



Joined: Apr 15, 2006
Posts: 297
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PostPosted: Wed May 25, 2016 2:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

You've measured the pots at 50% for 50k? Log pots would certainly skew things; no mention of the provenance.

Many modern leds can be starved down considerably for adequate lumens for panel work.


R
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sharkattackeddie



Joined: May 24, 2016
Posts: 6
Location: UK

PostPosted: Tue May 31, 2016 6:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your suggestions everyone. I came back to this after a few days away and it seems to work. Perhaps it somehow sensed I had got my metre out?
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