RX3 Sidestand Safety Switch - Part II
In Part I I described wiring up a sidestand switch and describing how it could be used to light up an LED when the sidetand is down, plus the basics of a scheme to shut the bike down if you try to ride away with the sidestand down. That scheme involves detecting the following three conditions are met:
- The bike is in gear AND
- The clutch is out AND
- The sidestand is down Unless all three conditions are met, the bike should run as normal. The kill switch will work as normal under all conditions.
As mentioned earlier, the bike generates it's own 5v logic HIGH signals when conditions (1) and (2) are met. The light purple wire which connects to the clutch switch is at a logical HIGH (4.5v) when the clutch is out AND the bike is in gear. If clutch is pulled in then the signal become a logical LOW, similarly if the bike is in gear the signal is also a logical LOW whether the clutch is in or out.
A sidestand switch can be wired to generate a logical HIGH signal when the sidestand is down as shown below.
The sidestand HIGH and Clutch/Gear HIGH are input to a two-input NAND gate, which forces the output of the Gate LOW. This gate then drives a relay module which opens the relay on a LOW input and kills the engine.
The NAND gate can be implemented in CMOS logic using a 4011 chip, or you can use some sort of PIC (Peripheral Interface Controller) chip - essentially a simple computer. I used a PICAXE 8M2. The advantage of using a PIC (Picaxe, Arduino etc.) is that you can do some software signal conditioning to filter out glitches and spikes, plus you could at some point in the future use it for other control functions. The disadvantages are extra complexity and that you need to be able to program it. The single CMOS 4011 is cheaper and requires no programming.
Note that the components here are 5v TTL logic (that's dictated by the existing signal from the clutch switch), you need to add a regulated 5V supply which you can easily derive from the bikes nominal 12v system using a simple 7805 5v regulator chip 7805 linear regulator IC or a prebuilt 12v to 5v converter module
. Strictly speaking there is a difference between chassis (battery) ground (ECU pins J2-2 and J1-9, GND), and the digital ground used by the ECU (J2 Pin10 5vRTN) but this shouldn't really give rise to problems in this application. However it's something to be aware of if problems ever do surface. There can be a small voltage difference between the two.
The Relay Module can be purchased from eBay for a few dollars. It has a relay and a driver transistor on it (some also have opto-isolators) and it switches the relay when the logical signal to the input is LOW (some can switch on LOW or HIGH). They are very easy to find on eBay and only cost a few dollars.
The system presented here is designed to be "fail safe", meaning that if all of the added electronics fail, the relay stays closed and the bike operates as normal, with no sidestand protection, the default clutch and gear restrictions on starting the bike and a normally operating kill switch. The entire system could be also bypassed by wiring a SPST switch across the relay and the bike would operate as it did before any additions.
I have not given specific point to point wiring instructions for the logic gate or microcontroller. If you don't know enough about electronics, wiring and circuit construction to put this system together without further help, I'd suggest you'd probably be much better off sticking with the simple warning light circuit originally described on the first page of this article.
DISCLAIMER: If you decide to add such a system to your bike, you must take full responsibility for any damage to the bike's electronics and any accident that results from operation of the electronics you have added. I'm simply presenting the outline of one way to add a sidestand cutout system to the bike. I take no responsibility for what you do with this information and I accept no liability for any damage caused for whatever reason if you modify your bike in any way.
