Jump to content

DOUT to CV with R-2R Ladder


Navicat

Recommended Posts

This is a resistor ladder on a Dout module that can produce Controlable Voltage that midibox sequencers can handle

 

;; DOUT 160k 
;; D7 ---o---/\/\/\---* 
;; 80.6k | 
;; D6 ---o---/\/\/\---* 
;; 40.2k | 
;; D5 ---o---/\/\/\---* 
;; 20.0k | 
;; D4 ---o---/\/\/\---* 
;; 10.0k | 
;; D3 ---o---/\/\/\---* 
;; 5.1k  | 
;; D2 ---o---/\/\/\---*----CV Out-----------------------------------o ( 0v <----> +5v )
;; 220 Ohm 
;; D1 ---o---/\/\/\--------o free assignable trigger 
;; 220 Ohm 
;; D0 ---o---/\/\/\--------o another free assignable trigger

__________________________________________________________________________

 

What i wanna ask here is..

 

How can i use a shift register with a resistor ladder as that.. but with higher voltages.. i need to go from 0 to +15v

I need to use a different from 74HC595 that DOUT uses or is there another way?

I saw something similar before but i am not so sure.. maybe a TL074 can do the job like that in this image:

 


cv_ladder.png

 

Regards, Tilemachos

Edited by Navicat
Link to comment
Share on other sites

Thank you for your answer!

 

I know about Aout_LC and is really similar to that i want!

But i need something different and i am really sorry i did not explain!

 

What i wanna build is a module with with up to 8 CV channels that i will use to control the velocity on a TR-808 clone...

 

Velocity on a TR-808 is a Trigger pulse of 1ms width with voltage from +5 and +15

 

Here is my idea taken from another project.. will this work?

 

cv_ladder_808_velo.png

Link to comment
Share on other sites

To get higher voltage, you need to configure the tl074 for some gain.

You do this by adding a voltage divider to the feedback loop of the op-amp.

eg. 20k between output and "-" and 10k between "-" and GND.

 

If you don't need those pulses at the same time, this could work.

You need to feed  A and B with address bits, though. C can stay low, since you only use 4 Outputs.

Link to comment
Share on other sites

That's what i meant.

 

Do you need any voltages between +5 and +15, or just those two values?

If it's just 5V and 15V, there is an easier soulution:

You could use two DOUT pins per instrument, one going directly to the trigger-in and another going to a ULN2803 or similar, so it gets amplified to 15V and then to the trigger-in.

Link to comment
Share on other sites

Thank you very much for help me understand this!!!

 

No i need any voltages between 0 and 15 volts with as much as high resolution i can get.. but 8-bit is ok!!

Here is an example!! Thanks for your help!

 

0 volts in = 0 volts out

1 volts in = 3 volts out

3 volts in = 9 volts out

3.5 volts in = 10.5 volts out

until i go up to

5 volts in = 15 volts out

 

That's amazing!!!

 

Regards Tilemachos

Link to comment
Share on other sites

This has a gain of 1.5, to get a gain of 3 2k and 1k have to be switched.

Since the op-amp will never have to put out negative voltages, you could connect its negative supply to gnd instead of -15V.

You will need a little more than +15V on the positive supply, because else the op-amp can't reach +15V on its output.

Link to comment
Share on other sites

Ok i made a schematic for an 8x CV OUT and i need verification.. The R-2R ladder values are 20k and 10k.

One more thing i wanna ask is.. Can i drive J19 on mbhp_core_stm32f4 to work as the J8/9 and connect more Dout and DIN chain?

 

Here is the schematic for my DOUT with DAC and op-amps to get signal up to +15V :

 

http://www.docdroid.net/ri8z/dout-cv.pdf.html

 

Regards Tilemachos

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...