hey there!
So I want to build a little sequencer box, powered by a 9V battery. In it’s core it should consist of four CD4017-based sequencers (i used eddy bergmans sequencer schematic), each with 4 steps, and a sequential switch to switch between them. (i’d like to add two other CD4017 sequencers as trigger sequencers, but that’s another topic i’m not at yet.)
I’m only working with dc voltages, so I’m only using one 9V battery. Because this limits my range to 0-9V, the doepfer-151 schematic seemed like a good catch, because its flaw of being limited to -8V to +8V in its input/output range wouldn’t bother me. but i have some questions about this:
can i simpy connect all the connections that go to -8V to GND or do i have to make any changes to the schematic in order for it to function properly?
what is the purpose of the D1-D10 Diodes, right in front of the input/output resistors?
when i breadborded the circuit, i placed the diodes D11-D14 in the opposite direction, because they arent lighting up if placed like in the schematic. now one is always on and the others are changing in (binary?) patterns (it also made more sense to me? im pretty sure i’m wrong in this case, but i’d like to know why and how to fix it…)
Protection. If the jack gets connected to a voltage source much higher than +8 V (that is, 8 V plus Vf, the diode forward voltage) then the upper diode of the pair will conduct and limit the voltage on the CD4052 pin to 8+Vf. Likewise if it’s connected to a voltage source below -8-Vf the lower diode will conduct and limit the negative voltage on the pin.
I don’t see where it says what those diodes are but Schottky diodes such as 1N5017 will have lower forward voltage and so place tighter limits. Per the datasheet, absolute maximum voltage input is -0.5V to VDD +0.5V referred to Vss so a forward voltage of less than 0.5 V would be desired.
So then the first question:
Looks like that would work. In that case the lower diodes in each pair would limit negative voltages on the IC pins to -Vf.
I don’t understand the orientation either. As I understand it when the CD4052 receives a binary number on pins 9 and 10 it connects the corresponding one of Y0-Y3 to Y and of X0-X3 to X. X is +8 V, so the LED cathode should be toward ground, I think. Only one should be on at a time, the one corresponding to the binary number on pins 9 and 10.
thanks for the explanation! so because i’m hardwiring the outputs of the baby4 sequencers to the input and they won’t get anywhere outside of the maximum voltage range, i can simply skip them?
I just checked niklas rönnbergs modified schematic and he changed the orientation too. so the orientation in the döpfer schematic is probably wrong.
Yeah, it was my fault. I checked the breadboard again and messed the connections up. Everything works fine now and as it should! Thanks for your help!