DR Racing Products

Transistor Controllers
Frequently Asked Questions - And Answers!

 There is so much more to a controller than how many bands or whatever whizbang features it has. If the focus by manufacturers and consumers is only on number of bands or what new widget it has, progress in other important areas will be neglected. I have seen this in other areas of endeavors where the numbers-race-madness blinds people from what is a genuine technological advancement.

When shopping for a controller, consider all the major brands, Ask questions, Call the manufactures and listen to the reasons for the things they do. Don't just buy what some hot shoe recommends.

Here are some questions that need to be asked so you can cut through the clutter:

1. Is the controller overly complex and does its complexity have a real advantage or just a marketing one?

2. What effects does the complexity have on reliability?

3. Is the potential improvement that complexity adds so slight that it is not worth doing?

It is important to understand that controllers operate under a very harsh environment and must be very rugged electrically to survive.

4. Does the controller have any multi-pin (more than three) I.C. chips?

Most of these devices have low voltage ratings which can cause problems with the harsh environment in the track, car and controller circuit. I have had first hand experience with this when I used a 30 volt rated schottky barrier diode and I started having failures of this part. I went to a 100 volt rated rectifier diode and the problem went away. So what's happening? The motor's inductance in the circuit is generating high voltage spikes and oscillations. I question the wisdom of using these devices (chips) when a very good controller can be built without them.

5. Is the mechanical trigger mount to wiper contact design flimsy, inaccurate and difficult to repeat?

6. Does the controller have one or two power transistors to ensure enough amperage headroom and reduce voltage drop at full transistor power?

7. Does the controller have individual bands and resistors that allow it to be re-curved?

8. Does the controller have a fuse on its transistor output thereby saving an unnecessary repair?

9. Does the controller have the ability to load regulate? (the sensitivity feels about the same when you change to a different wattage motor). Controllers without this can sometimes be a pain to get it to feel right and require more adjusting to get things right.

10. Does the controller have no dead band?

Without a dead band if the trigger stop contacts are fouled with dirt not only will you lose brakes but it will also fail to turn off the transistors - making for an even harder wall blast.

Back to the band number controversy. Yes, I could of put more bands on my new 18 band board but I was concerned that if the bands became too narrow that the glue that bonds the copper to the board might fail over the long term. Also, the gaps between the bands need to be big enough to reduce problems with conductive dirt bridging the gaps.

It's important to understand that as you increase the number of bands the voltage increase from band to band gets very small thereby reducing the chance of upsetting the car. Also, your trigger finger only has so much precision to it in the first place.
This is where a smooth trigger is very important which makes it easier to control with your finger. I've had racers ask me if ball bearings really help and my answer is a definite yes. After building thousands of controllers with and without ball bearings, the controllers with ball bearings simply feel better. The trigger returns easier, it has less play in it, and it's definitely easier for your finger to control the trigger.

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