Author Topic: Where to find rotary encoder?  (Read 8724 times)

DaveTV

Where to find rotary encoder?
« on: May 11, 2004, 09:19:05 PM »
I'm looking to find a 4-bit 16-position rotary encoder for program switching on the Alesis AL3201B reverb chip. I was able to find one at Allied Electronics (Clarostat 510 series) but was wondering if anyone knew of any other vendors, obscure or otherwise.

Peter Snowberg

Where to find rotary encoder?
« Reply #1 on: May 11, 2004, 11:32:54 PM »
For a couple of others try Alpha and Grayhill

Best of luck!

There are also other styles like rotary DIP switches which Mouser carries, just don't step on them. ;)

Take care,
-Peter
Eschew paradigm obfuscation

Paul Perry (Frostwave)

Where to find rotary encoder?
« Reply #2 on: May 12, 2004, 09:32:32 AM »
I use rotary encoders from Alps. But I think ther eare 2 basic forms of "rotary encoder", one like a switchg with say 16 positions that puts out a digital pattern on the outputs according to the absolute rotatary position, and the other just puts out a pulse as it goes foward or back, so it can count up or down. (I use the former to set midi channel in a midi cv unit, and the latter to select algorithm in my Sonic Alienator bitcrusher).

DaveTV

Where to find rotary encoder?
« Reply #3 on: May 12, 2004, 01:57:02 PM »
Thanks Paul. I'm new to working with digital chips so I'm still trying to piece all of these things together.

I have noticed the two types of rotary encoder, absolute and relative, but I wasn't totally sure if I could use either one. The Alesis chip has 4 program pins that let you switch between the reverb programs by using a 4-bit encoder of some kind. The chip has 16 programs, so the pins receive 0000 to 1111 from the encoder. The programs are arranged in an numeric order that works best with a Gray code encoder, but I expect the order of the programs isn't that important.

Would a relative encoder work in this situation. I assume I would need one with 4 outputs for the chip's 4 pins. What else would work?

I've even thought of the possibility of using 4 small toggle switches mounted on the box to feed binary to the pins (like a makeshift dip). Would this work? My understanding is I'd need to feed voltage to the pins for "1" and no voltage for "0". Or does the "0" require at least a small voltage?

Peter Snowberg

Where to find rotary encoder?
« Reply #4 on: May 12, 2004, 03:10:48 PM »
Realitive encoders are more commonly called "quadrature encoders" and they won't really work for what you want. You need an absolute encoder or four toggles switches. :D

If you went the toggle switch route, the standard way for inputting digital data is to use a pull-up or pull-down resistor of something like 10K-22K that keeps the input at a known logic state. A switch is then used to connect the input to the opposite power rail.

If you use a gray code output, the programs will be arranged very nicely. If fact, I would absolutely suggest getting such an encoder just for layout.

Take care,
-Peter
Eschew paradigm obfuscation

DaveTV

Where to find rotary encoder?
« Reply #5 on: May 12, 2004, 04:29:35 PM »
Hi Peter. According to the chip's data sheet, the chip's recommended supply voltage is 5V and the logic input voltage appears to be 2.5V. I was planning on using a 5V regulator, and so a voltage divider with two 10k resistors should bring me to the logic voltage, yes?

After looking at the evaluation board schematic for the AL3201B, I've noticed that the rotary encoder doesn't seem to be connected to any power supply (unless I'm missing something). How does it work? I thought that it basically took a source voltage and channeled to out through it's outputs, on/off depending on the switch's position.

Paul Perry (Frostwave)

Where to find rotary encoder?
« Reply #6 on: May 12, 2004, 10:01:47 PM »
Quote from: DaveTV
I've noticed that the rotary encoder doesn't seem to be connected to any power supply (unless I'm missing something). How does it work?

just guessing (wildly) but, maybe it is wired so various switchen\s inside the encoder are shorting to earth, and pulling down various connected lines.

Peter Snowberg

Where to find rotary encoder?
« Reply #7 on: May 12, 2004, 11:16:03 PM »
The data sheet says that the minimum voltage required to register as a 1 is 2.5 volts, but it may be as high as Vdd. The data sheet also says that each of the program select pins is hooked up to a 30K pull-up resistor internally. With that the case, all you need to do is hook the pins to ground through the switch.

I don't know the make (almost 100% sure it's Alpha), but the Alesis Pico-Verb uses a 16 position encoder that is in the form factor of a 16mm. The part number is 280-S0041.

Take care,
-Peter
Eschew paradigm obfuscation

DaveTV

Where to find rotary encoder?
« Reply #8 on: May 13, 2004, 04:55:25 PM »
Thanks for all the help, guys. Yes, the Picoverb's encoder is the exact same one I have in my Nanoverb. However, I wasn't able to find the actual piece anywhere, even browsing through Alpha's web sit.

The 4-bit Clarostat 510 looks like it will do. Allied Electronics has it, but they have a minimum $25 order requirement, and the encoder is only about $4. I called them to see if they'd waive the $25 handling fee but instead they're going to send me the part as a free sample. Nice.

In fact, the same thing happened when I called to order the AL3201 reverb chip and the two A/D and D/A converter chips. The guy sounded a little disappointed that I wasn't ordering 10,000 units, but after a short conversation he decided to send me 2 of each for free. Can't beat free stuff.

Also worth noting is that Alesis Semiconductor became Wavefront Semiconductor a year or two ago (didn't know this). I had a little trouble tracking these chips down at first. The guy at Wavefront says they can't remove the old Alesis Semi site, which seems to still be the default site for these chips. All of the technical data is still the same, but Alesis is no longer selling these chips themselves.

Peter Snowberg

Where to find rotary encoder?
« Reply #9 on: May 13, 2004, 05:58:08 PM »
Interesting.... about a year ago I talked to the sales guy and the president and didn't hear anything about this. The wavefront domain is registered to the old president of Alesis-semi.

-Peter
Eschew paradigm obfuscation

DaveTV

Where to find rotary encoder?
« Reply #10 on: May 13, 2004, 08:12:37 PM »
Yeah, the guy at Wavefront was pretty up front about the change over. He said they were all the same people, just new name and location. Even the documentation for their chips is the same as on the Alesis site, just with the name changed on the .pdf files. The guy was concerned about people not being able to find their web site easily. Apparently the Alesis Semi site is on an internal server at Alesis and they don't have access to it anymore to close it down.

From what I understand, Alesis has been going through some hard times recently. This probably created a situation where for the semiconductor group felt they'd be better off on their own, especially if they developed the technology on their own.