Can we do this? (aka The DIY Cruise Control Thread)

[PatrickJohnson]

I'd love to see a schematic. I would be willing even to have some PCBs etched for people as drop-ins. Does this just drive the On/OFF LED? What about the SET light?

EDIT: I see you mentioned it can sense the difference between the switches, so I assume this drives both LED's. Again though, if you post the schematic I can etch actual circuit boards (instead of perfboard) for you or anyone else if there is interest.

[CTScott]

Originally Posted by PatrickJohnson

I'd love to see a schematic. I would be willing even to have some PCBs etched for people as drop-ins. Does this just drive the On/OFF LED? What about the SET light?

EDIT: I see you mentioned it can sense the difference between the switches, so I assume this drives both LED's. Again though, if you post the schematic I can etch actual circuit boards (instead of perfboard) for you or anyone else if there is interest.

It just drives the power LED. Because the switches are all paralleled together, the ADC is required to differentiate the on/off switch from the other three.

The problem with driving a SET LED, based on just the switch, is that there are too many conditions where you could press the switch, but not really be "set". Tonight I should have a chance to drop the schematic into ORCAD. If there was enough interest in the modules I figured I would do a run of boards.

[PatrickJohnson]

Originally Posted by CTScott

It just drives the power LED. Because the switches are all paralleled together, the ADC is required to differentiate the on/off switch from the other three.

The problem with driving a SET LED, based on just the switch, is that there are too many conditions where you could press the switch, but not really be "set". Tonight I should have a chance to drop the schematic into ORCAD. If there was enough interest in the modules I figured I would do a run of boards.

I see. pretty cool either way. I was thinking of just doing a cmos flip flop switch to run the LED. I figured I could use the connection made by the on/off to touch a flip flop circuit or a relay and reset it's state, turning on the LED. of course, that might be using a sledgehammer to drive a thumb tack :)

[CTScott]

Originally Posted by PatrickJohnson

I see. pretty cool either way. I was thinking of just doing a cmos flip flop switch to run the LED. I figured I could use the connection made by the on/off to touch a flip flop circuit or a relay and reset it's state, turning on the LED. of course, that might be using a sledgehammer to drive a thumb tack :)

I started off thinking I would use a flip flop, but you can't drive anything unless you change to a switch with a second set of contacts and you also have to maintain a high impedance to not confuse the ECM. The microcontroller is definitely overkill, but they are under $2.

[Sir A.Y. Atoyot]

For controlling an indicator light- has anyone considered a DPST switch for on-off? Wouldn't work for the stock cruise switch, of course, but it should be OK for the improvised setups. Too simple?

[CTScott]

Originally Posted by Sir A.Y. Atoyot

For controlling an indicator light- has anyone considered a DPST switch for on-off? Wouldn't work for the stock cruise switch, of course, but it should be OK for the improvised setups. Too simple?

With a DPDT switch you'd still need a circuit to toggle the LED on and off. The circuit becomes simpler (a flip flop using two transistors or one IC), but is still required, as the switch is a momentary input, rather than a toggled one.

[Sir A.Y. Atoyot]

Originally Posted by CTScott

With a DPDT switch you'd still need a circuit to toggle the LED on and off. The circuit becomes simpler (a flip flop using two transistors or one IC), but is still required, as the switch is a momentary input, rather than a toggled one.

I get it now.

If someone can come up with a tidy module to make this work, it could be a minor cottage industry. It should work with the OEM switch installations, as well as the improvised ones.

[CTScott]

Originally Posted by PatrickJohnson

I'd love to see a schematic. I would be willing even to have some PCBs etched for people as drop-ins. Does this just drive the On/OFF LED? What about the SET light?

EDIT: I see you mentioned it can sense the difference between the switches, so I assume this drives both LED's. Again though, if you post the schematic I can etch actual circuit boards (instead of perfboard) for you or anyone else if there is interest.

Here's the schematic:

[mg_xpower]

Nice work. Please consider the fact a car power supply is really "dirty". You'll have to take bursts and surges into account. I'd add a nice big elco to VDD (at least 100uF 35V) and a 100nF 50V X5R/X7R ceramic capacitor close to the controller.

Are you measuring battery voltage at p6 ? -> Add 100nF over R7.