daveq Posted June 23, 2004 Report Share Posted June 23, 2004 I need some help/ideas on how to switch between a set of potentiometers without needing to use relays. I don't know if it can be done or not. There is a common circuit that requires a series of pots (3 or more) to tweak. I'd like to be able to switch between two "banks" of potentiometers without using relays. The reason I'm not in favor of relays is power consumption - the entire circuit is battery powered. Is there any way to switch between the sets of pots using transistors or other low power devices? Quote Link to comment Share on other sites More sharing options...
daveq Posted June 23, 2004 Author Report Share Posted June 23, 2004 Someone mentioned the possibility of using a multiplexer 74HC4051 (use multiple chips) for this but something doesn't seem right about that. I thought those chips were designed to control logic / digital signals only and would not be able to switch a resistor in and out of a circuit. Any idea? Anyone? Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 23, 2004 Report Share Posted June 23, 2004 Any of those CMOS bilateral analog switching packages will work if your signal levels are compatible, or you could use discrete MOSFETs for higher levels. RG Keen uses a CD4051 in his Sing-Wah, and he's got a page on using the CD4053 for bypass switching and a Wah Controller that sequences a series of preset pots. That should get you started - the other options are opto-isolators, but they're generally a lot more expensive and current-hungry. HTH Quote Link to comment Share on other sites More sharing options...
daveq Posted June 23, 2004 Author Report Share Posted June 23, 2004 Lovekraft - thank you so much for getting me headed in that direction. Man, that RG Keen guy is incredible. His drawings of the CD4053 show SPDT switches but they are actually transistors (or networks of transistors, ...), right? He mentioned that when connected, the switches act like 150 to 500 ohm resistors. I think that should work fine for me - it will just mean that adjusting the pots to "0" will really be 150 to 500 ohms then, right? The pots are going to be large (around 100K) so losing a little on the low end shouldn't be a big concern. Now my biggest concern is whether or not that accomplishes my ultimate goal which is saving board space. I was trying to avoid replicating the circuit that the pots tie into since they will be identical and will never need to operate at the same time. It looks like I might end up chewing up that space with the chips/components needed to switch the pots though. That's great information though - exactly what I was after. Thanks again! Quote Link to comment Share on other sites More sharing options...
lovekraft Posted June 23, 2004 Report Share Posted June 23, 2004 OK, I missed the part about saving board space - here's a couple of other ideas: Audio Switch Notes Programmable FX switcher (also from RG) Using discrete FETs might use less real estate - the only trick is biasing them correctly, since they vary so widely from piece to piece. Again, hope these are helpful. FWIW, Mezza Boggie uses discrete JFETs for most of their audio switching. Quote Link to comment Share on other sites More sharing options...
daveq Posted June 24, 2004 Author Report Share Posted June 24, 2004 Thanks again - that's great information. Quote Link to comment Share on other sites More sharing options...
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