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 Forum index » DIY Hardware and Software » YuSynth
Yusynth clock divider LEDs on
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micromusic



Joined: May 05, 2014
Posts: 61
Location: england

PostPosted: Sat Jul 20, 2019 5:32 am    Post subject: Yusynth clock divider LEDs on Reply with quote  Mark this post and the followings unread

Hi

Just wiring and testing the Yusynth clock divider I am making and have a small problem with the LEDs which are never fully off

I am using white LEDs and have changed the value of R12,24 and 36 to 15k which has toned the brightness down but they still glow quite bright when no signal is through the circuit, all components are as per the schematic, all transistors are 547Cs

Which component changes do I need to make to get nice flashie LEDs?

thanks


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Grumble



Joined: Nov 23, 2015
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PostPosted: Sat Jul 20, 2019 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Due to the diodes like D5 and resistor R9 the output of the 4017 can never pull the base of Q3 to gnd level. Try substituting R10 with a diode 1n4148 with its cathode towards the base of Q3. It will give an extra voltage drop and could help you switching off the led.
No need to try all three channels at once.

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micromusic



Joined: May 05, 2014
Posts: 61
Location: england

PostPosted: Sun Jul 21, 2019 11:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Grumble tried that but it made no difference but thanks for the suggestion

Put a 5.1 volt zener in series with the LEDs and that made a difference as only one of the three are now glowing but I figure that limits the output as well to 5v

Thanks
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Sun Jul 21, 2019 11:37 am    Post subject: Reply with quote  Mark this post and the followings unread

The diode seemed like a good suggestion but those white/blue LEDs really hardly need any current to light up.
Another thing you could do is use a seperate logic chip just to drive the LEDs. The current is low anyway so you could use any CMOS chip.
I probably go for a CD4093 Quad NAND gate myself or maybe a CD40106 and use 2 gates in series per LED.

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Grumble



Joined: Nov 23, 2015
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PostPosted: Sun Jul 21, 2019 12:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Check the voltage of the anode of the led with an oscilloscope, make sure it’s a DC voltage otherwise the diodes D4 etc are backwards which makes the clock pulse light up the led’s.
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micromusic



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PostPosted: Mon Sep 16, 2019 9:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Finally got back to this module to fault find and noticed a trannie the round way round, I must of looked at this a hundred times!!!!
I now have a dual clock divider with nice on and off LEDs it make a very nice sub oscillator and works with Tri Square and Saw waveforms, doesn't seem to like Sine waves maybe no sharp edges for the trigger circuit
Thanks for all your suggestions
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