woodslanding
Member
I'm trying to do something that may or may not be possible. I'm trying to turn a set of actual hammond drawbars into a midi controller. (Well, actually I've at least proven it's possible to do it badly!)
The way Hammond drawbars work, each of the 9 drawbars can be pulled out to one of 8 different positions. As it does so, it makes contact with each of 8 buss bars, which run perpendicular to the drawbars. In the process, it increases the volume of one oscillator from zero to maximum in 8 increments. The 9 oscillators make up the tone of a note.
So what I did was put a 1k resistor between each buss bar, and attached the rear buss bar to ground, and the front buss bar to voltage. Each drawbar has a wire attached at the rear that then becomes a wiper. I attached each one to an analog input.
It actually works, but there is an issue. I tested it by pulling each drawbar all the way out, and then pushing it back in. This works great. Then I installed it in the cabinet. But in use, I discovered that when one or more of the bars is in a midway position, the movement of other bars causes the voltage to fluctuate.... oops. I expected crosstalk, but I neglected to consider it would be minimized at the extremes. I guess I'll be opening it back up.
Now I'm wondering if someone with greater understanding of electrical engineering could tell me if there is likely to be a practical fix for this. If not, I have a set of 10k (cheap! plastic!) drawbar pots I could retrofit. But if there's some magic I could work by wiring in a few resistors or some other arcane component I don't even begin to understand (I don't know, DIODES????) ...well it's worth asking, I guess.
Thanks in Advance!
-eric
The way Hammond drawbars work, each of the 9 drawbars can be pulled out to one of 8 different positions. As it does so, it makes contact with each of 8 buss bars, which run perpendicular to the drawbars. In the process, it increases the volume of one oscillator from zero to maximum in 8 increments. The 9 oscillators make up the tone of a note.
So what I did was put a 1k resistor between each buss bar, and attached the rear buss bar to ground, and the front buss bar to voltage. Each drawbar has a wire attached at the rear that then becomes a wiper. I attached each one to an analog input.
It actually works, but there is an issue. I tested it by pulling each drawbar all the way out, and then pushing it back in. This works great. Then I installed it in the cabinet. But in use, I discovered that when one or more of the bars is in a midway position, the movement of other bars causes the voltage to fluctuate.... oops. I expected crosstalk, but I neglected to consider it would be minimized at the extremes. I guess I'll be opening it back up.
Now I'm wondering if someone with greater understanding of electrical engineering could tell me if there is likely to be a practical fix for this. If not, I have a set of 10k (cheap! plastic!) drawbar pots I could retrofit. But if there's some magic I could work by wiring in a few resistors or some other arcane component I don't even begin to understand (I don't know, DIODES????) ...well it's worth asking, I guess.
Thanks in Advance!
-eric