DickB
02-08-2009, 09:11 AM
I want to try adding trim tab controls to my steering wheel. I have factory-installed Bennett tabs with the tab switch on the dash to the right of the steering wheel. Outdrive trim control is on the throttle, which I find perfect. However, I have to take my right hand off the throttle to adjust the tabs. I think tab switches on the left side of the wheel, which could be operated by thumb, would work well – hands remain on wheel and throttle. I'd like to give that a try.
I don't like the idea of messing with clock springs or brushes to make wired electrical connections through the wheel. I think wireless is the way to go.
Livorsi has a wireless setup with a radio transmitter in the hub of the wheel and switches mounted to the wheel. I considered this, but rejected it for several reasons: it's expensive, Livorsi insists upon doing it for you, and it's irreversible without replacing the wheel. Lectrotab has a wireless switch setup, but it's meant to be attached to the dash and draws power through a wired connection, so that’s out. I like the ergonomics of the Insta-Trim tactile switch. I imagine a smaller version of that switch mounted to the spoke of the wheel, integrated with a wireless transmitter. I think it would be easy to slide a thumb over and raise or lower one or both tabs without diverting the eyes with a switch like that.
I’m implementing this concept using two devices: a switch assembly with a battery-powered wireless transmitter for the wheel and a wireless receiver/controller behind the dash that attaches to the Bennett wired switch.
For the wireless link I’m using Linx components. Linx makes easy-to-use radio-frequency (RF) modules, ICs, and component building blocks, as well as a few complete transmitters and receivers.
The receiver/controller, mounted behind the dash, receives the RF signal from the integrated switch on the steering wheel. It decodes the RF signal and simulates Bennett switch closures to the stock hard-wired system. The receiver/controller employs a Linx receiver module, decoder IC, some discrete components, and relays. The receiver/decoder converts the port/starboard up/down button presses into the proper pump active/pump reverse and port/starboard valve contact closures. I’m using common automotive relays in the controller, as these are capable of handling the Bennett system current loads and are relatively inexpensive. I have already assembled a breadboard proof-of-concept prototype, and have a few parts on order to complete a working prototype. I expect to have this completely built and working in one to two weeks.
Linx offers a few complete key fob transmitters for about $20 that are functionally perfect for this job. You probably have a fob like this in your pocket for your car. The fob uses small rubber switches that are not suitable for this application due to their size, shape, and tactile characteristics. I’m using the guts of the fob: a circuit board with battery holder and battery. I’m adding a circuit board on top of the Linx board that contains four tactile switches. On top of these I’m placing custom rocker switch caps. These components are all held in a custom enclosure.
I started working on the enclosure this weekend, and got much farther along than I expected. I hit on the idea of using PVC plumbing materials from the local hardware store for this. The plastic facilitates RF transmission, and PVC is relatively easy to work with basic hand tools. The enclosure is a pipe end cap and the switch caps are harvested from the side of larger one, making use of the sidewall curvature. The switch/transmitter is about 2” in diameter and 1” tall. It’s a bit bigger than it needs to be, as the PVC is over 1/8” thick, way more than it needs to be. I think the diameter is about right. Smaller switch caps would probably be harder to use. But the enclosure could be a lot thinner (not so tall), especially if a single, custom circuit board were used rather than the standard Linx board and added switch board.
I think a billet aluminum enclosure would look sharp, but this is beyond my current skills and tool set (anyone interested?). As the Linx transmitter guts employs an integrated antenna, the case needs to allow a path out for the RF energy. I think a billet aluminum case with plastic switch caps and a plastic base would work, especially if the base is offset or overhangs the metal spokes of the steering wheel, which it probably will in my case. The Linx RF components have a range of up to 1000 ft with proper antennas. Since I will be operating at only a few feet at most, the RF transmission can be heavily attenuated and still have plenty of margin to operate. So an aluminum case is a possibility. A small external antenna – just a length of wire – could also be employed.
I’m attaching some photos and hand drawings (I’m not CAD capable yet) of the switch/transmitter components.
You can probably see that a wide variety of sizes and shapes of the switch caps and case could be used. For example, the new Bennett euro or the Livorsi switch shapes could be emulated if that were preferred.
There was a thread a while back lamenting the fact that many projects are worked in secret and then sprung on the board when complete, as opposed to displaying and discussing works in progress. That thread prompted me to share my current project as a work in progress. Comments are welcome.
I don't like the idea of messing with clock springs or brushes to make wired electrical connections through the wheel. I think wireless is the way to go.
Livorsi has a wireless setup with a radio transmitter in the hub of the wheel and switches mounted to the wheel. I considered this, but rejected it for several reasons: it's expensive, Livorsi insists upon doing it for you, and it's irreversible without replacing the wheel. Lectrotab has a wireless switch setup, but it's meant to be attached to the dash and draws power through a wired connection, so that’s out. I like the ergonomics of the Insta-Trim tactile switch. I imagine a smaller version of that switch mounted to the spoke of the wheel, integrated with a wireless transmitter. I think it would be easy to slide a thumb over and raise or lower one or both tabs without diverting the eyes with a switch like that.
I’m implementing this concept using two devices: a switch assembly with a battery-powered wireless transmitter for the wheel and a wireless receiver/controller behind the dash that attaches to the Bennett wired switch.
For the wireless link I’m using Linx components. Linx makes easy-to-use radio-frequency (RF) modules, ICs, and component building blocks, as well as a few complete transmitters and receivers.
The receiver/controller, mounted behind the dash, receives the RF signal from the integrated switch on the steering wheel. It decodes the RF signal and simulates Bennett switch closures to the stock hard-wired system. The receiver/controller employs a Linx receiver module, decoder IC, some discrete components, and relays. The receiver/decoder converts the port/starboard up/down button presses into the proper pump active/pump reverse and port/starboard valve contact closures. I’m using common automotive relays in the controller, as these are capable of handling the Bennett system current loads and are relatively inexpensive. I have already assembled a breadboard proof-of-concept prototype, and have a few parts on order to complete a working prototype. I expect to have this completely built and working in one to two weeks.
Linx offers a few complete key fob transmitters for about $20 that are functionally perfect for this job. You probably have a fob like this in your pocket for your car. The fob uses small rubber switches that are not suitable for this application due to their size, shape, and tactile characteristics. I’m using the guts of the fob: a circuit board with battery holder and battery. I’m adding a circuit board on top of the Linx board that contains four tactile switches. On top of these I’m placing custom rocker switch caps. These components are all held in a custom enclosure.
I started working on the enclosure this weekend, and got much farther along than I expected. I hit on the idea of using PVC plumbing materials from the local hardware store for this. The plastic facilitates RF transmission, and PVC is relatively easy to work with basic hand tools. The enclosure is a pipe end cap and the switch caps are harvested from the side of larger one, making use of the sidewall curvature. The switch/transmitter is about 2” in diameter and 1” tall. It’s a bit bigger than it needs to be, as the PVC is over 1/8” thick, way more than it needs to be. I think the diameter is about right. Smaller switch caps would probably be harder to use. But the enclosure could be a lot thinner (not so tall), especially if a single, custom circuit board were used rather than the standard Linx board and added switch board.
I think a billet aluminum enclosure would look sharp, but this is beyond my current skills and tool set (anyone interested?). As the Linx transmitter guts employs an integrated antenna, the case needs to allow a path out for the RF energy. I think a billet aluminum case with plastic switch caps and a plastic base would work, especially if the base is offset or overhangs the metal spokes of the steering wheel, which it probably will in my case. The Linx RF components have a range of up to 1000 ft with proper antennas. Since I will be operating at only a few feet at most, the RF transmission can be heavily attenuated and still have plenty of margin to operate. So an aluminum case is a possibility. A small external antenna – just a length of wire – could also be employed.
I’m attaching some photos and hand drawings (I’m not CAD capable yet) of the switch/transmitter components.
You can probably see that a wide variety of sizes and shapes of the switch caps and case could be used. For example, the new Bennett euro or the Livorsi switch shapes could be emulated if that were preferred.
There was a thread a while back lamenting the fact that many projects are worked in secret and then sprung on the board when complete, as opposed to displaying and discussing works in progress. That thread prompted me to share my current project as a work in progress. Comments are welcome.