15 replies to this topic

[dalek]

I like my Third Eye controller because of it's light weight, thin light cord and good trigger feel.

 

However, as the other guys where I race know, adjusting the brakes for any given car, can be difficult because the amount of braking changes a lot with only a small amount of knob turn when between 4 and 4 1/2 on the dial.

 

To solve this problem, I modified my Third Eye by moving the brake pot (a 5K pot) from it's original position and installing it in the middle of the board, then putting a 500 ohm pot in the brake position and wiring them in series.  

 

So to adjust the brakes, the 5K pot (what I would call the range pot) is adjusted to bring the 500 ohm pot (the brake pot) into range so it can be used to fine tune the brake setting.  

 

The knob on the range pot has detents so it makes the pot act like a rotary switch which is ideal for this type setup.

 

This past Friday I used the controller and got the impression that the range pot will stay in the same position for most of the cars we race and if a change is needed, it won't be more than a click or two.

 

 

[Bill Seitz]

I haven't explored how Third Eye wires the brake pot, but likely V+ is connected to one end and ground to the other. The pot can then select a voltage between V+ and 0 to turn on the brake FET. Over the years, MOSFET's have been optimized for their major role as switching devices, and for minimum loss, designed to turn on rapidly above their minimum threshold voltage. The FET's I'm currently experimenting with turn on at around 2 volts and are 99% turned on at less than 6 volts. Most MOSFET's are specified to be 100% on by 10 volts. For all practical purposes, the pot range from 6 volts to V+ (12-14 volts) doesn't change the brake response, and the pot range from 0-2 volts doesn't turn on the brakes at all. So as you've noticed, the actual useful adjustment range from no brakes to 100% brakes is less than half the pot travel and can vary with the track voltage. As you've done, adding some additional resistance in the circuit helps put the brake pot into the useful narrow voltage range where it has greater adjustment effect.

 

This same phenomenon with FET's also effects a FET throttle circuit, and Third Eye has some additional circuitry in their controllers to accommodate this. It's curious why the same additional circuitry wasn't used in the brake function.

[gatormark]

Dale what are the three dipswiches for marked TH? I see your are all in the down position.

[Bucky]

Not trying to step on Dales toes, but they adjust the throttle curve. My understanding is that they arent sequential so moving any of the three to the up position has the same impact. Any 2 up increases the curve from 1 up, and 3 up is the steepest curve.

[gatormark]

Sorry, there are four. What is the gain by having them in the up position ie faster response?

[gatormark]

Just spoke to the owner,he cleared it up. Very nice guy

[Ben Naelitz]

would adding a resistor to the brake wire and connect that to the brake hookup serve the same purpose?

[dalek]

would adding a resistor to the brake wire and connect that to the brake hookup serve the same purpose?

No because you would only be adding resistance to the brake circuit which means you would never be able to have full brakes.

It would not be addressing the issue of the brake adjustment sensitivity.

[rmjlmartin]

would adding a resistor to the brake wire and connect that to the brake hookup serve the same purpose?

A Third Eye is also an electronic controller, which needs a ground connection to work properly. It gets that ground connection through the red (brake) track connection, so adding a resistor to that connection might make the controller do odd things. I've never tried it, so I don't know exactly what the effect might be, but it wouldn't work as intended.

[dalek]

I received a request for close-up photos so the wiring mods can be seen better.

 

But also I want to say that I modified a fellow racers 3rd Eye with a 1k factory pot, instead of the 500 ohm pot that I put on my 3rd Eye, and the results, in regard to significantly reducing the touchiness of adjusting the brakes, has been what we feel is satisfactory.

 

The 500 that I put on my 3rd Eye was the smallest 500 I could find but it is bigger than the factory pots, and getting it installed required quite a bit of modification.

 

The next time I modify the brakes on a 3rd Eye, I'm going to replace the 5k factory pot with a 1k factory pot and try a Bourns 3352W-1-502LF pot as the middle knob but just use double sided tape to install it on the back side of the board instead of drilling a hole in the board.

 

 

[dalek]

If anyone wants to do the 1k brake mod, the factory 1k pot is a Taiwan Alpha RV120F-20-15F-B1K Potentiometer.

[Joe Maxey]

If anyone wants to do the 1k brake mod, the factory 1k pot is a Taiwan Alpha RV120F-20-15F-B1K Potentiometer.

Pm sent

[dalek]

Here is a photo of the mod I mentioned in posts 10 and 11.

 

The little potentiometer is a 5K and is held in place with double sided Gorilla tape so no hole was drilled through the board.

 

The new main brake pot is a 1K (replacing the original 5K) so now adjusting the brakes is 5 times less touchy. 

 

In the photo, laying on the table above the controller, is a view of the back side of one of the little 5K pots.  I put just a tiny amount of grease on the end of the shaft (the dark spot in the center of the back side of the pot) so it wouldn't stick to the double sided tape when the knob is turned.

 

In regard to the wiring of the two pots, I believe the photo shows the wiring well enough so you can see how the pots are in series.

 

The 1K pot is a Taiwan Alpha RV120F-20-15F-B1K.  It's identical to the Sensitivity pot.

 

The little 5K pot is a Bourns 3352W-1-502LF.  I got it from Mouser Electronics, their part number is 652-3352W-1-502LF.

 

[dalek]

BTW:  Removing the original 5K brake pot is easy.

 

Pull the knob off (it might be on pretty tight so prying from underneath it might be necessary to get it started) then remove the nut and washer.

 

Turn the controller over so you can gently press the shaft of the pot straight down on the table.  

 

While doing so, use a wide soldering iron tip, with plenty of solder melted on it, to get the solder on all 3 pins of the pot melted at the same time and the pot will pop right out.

 

[Joe Maxey]

BTW:  Removing the original 5K brake pot is easy.
 
Pull the knob off (it might be on pretty tight so prying from underneath it might be necessary to get it started) then remove the nut and washer.
 
Turn the controller over so you can gently press the shaft of the pot straight down on the table.  
 
While doing so, use a wide soldering iron tip, with plenty of solder melted on it, to get the solder on all 3 pins of the pot melted at the same time and the pot will pop right out.
 

It worked perfectly! Thanks for the info. It took me 5 minutes to do the upgrade.

Thx!

[dalek]

Good to hear.