how much juice

for you electrical gurus..

Is 4.5 volts enough to trigger the pull down coil in a 30 amp relay? I have 4.5 volts in the brake wire, key on engine off. Relay is used to ground the brake wire to the Rosta cruise which works great but occasionally drops out as if the brakes were applied. Perhaps a spike, possibly when the RR turns on?

opinions plz..

lnewlf said:

for you electrical gurus..
Is 4.5 volts enough to trigger the pull down coil in a 30 amp relay? I have 4.5 volts in the brake wire, key on engine off. Relay is used to ground the brake wire to the Rosta cruise which works great but occasionally drops out as if the brakes were applied. Perhaps a spike, possibly when the RR turns on?

opinions plz..

Click to expand...

Where are you measuring 4.5 volts? Between the brake wire and ground? That's weird. Sounds like you might have the relay coil between 12V and the brake line, or something.

Relay coil should be between brake wire and ground. Ideally, the relay should have its moving contact connected to the Rostra brake sensor wire, the "normally made" contact connected to ground, the other contact to 12V, so when the brakes are off the sensor wire is connected to ground, when the brakes are on, it "sees" 12V.

4.5 volts between brake wire and ground-jumps to 12.5 when brakes are applied....not uncommon if LED lights are somewhere in the circuit.. tap off the brake wire to pulldown coil and CC sensor wire connected as above... is the 4.5 enough to occasionally energize the pulldown coil, especially if there is a surge?

Depends on the relay in question

Agreeing with Fred and adding a bit more information.

Relays have a characteristic called pull-in voltage. This is the minimum voltage across the coil at which the relay coil develops enough magnetism to actuate the contact arm and close the relay contacts. The pull-in voltage will vary from relay design to relay design. A Bosch 12 volt headlight relay may pull in at a different voltage than a Hella relay. The pull-in voltage range is commonly 1/2 to 2/3 of the operational voltage (12 VDC) which would be approximately 6 to 8 volts.

Conversely, this may also be specified as a drop-out voltage, when the voltage drops below 6 volts there is no longer enough magnetism to hold the contacts closed and so the relay contacts open.

If the 4.5 volts is there with LEDs and no relay (not clear from the OP's post), it will be very nearly zero with the relay. It only exists because a low current is used by the CC (and by the bike's ABS computer) to check the brake wire connection is good, expecting to "see" the very low resistance of the bulb filaments to ground.

Put the relay coil there, it will be much lower than 4.5, there's certainly not enough current to energise the relay.

that makes sense...I have 4.5 in the brake wire with LEDs and no relay...connecting the relay and checking at the relay coil terminal I have .1 volt...

must be another reason for the occasional drop out..

CC is designed for a much heavier vehicle with less power/weight ratio-the FJR- throttle response [abrupt] may be more than the CC can handle...the higher the speed setting, the better it works...ran perfectly for an hour and a half at 80 mph yesterday..

Is the Rostra cruise similar to the Audiovox CCS-100?

If so, which position is dip switch # 7 ?

I had "dropout" problems with my CCS-100 until changing the #7 dip switch to whatever position it wasn't.

On the Gen I bikes, dip switch #7 "on"

On some of the Gen II bikes, dip switch #7 "off"

kballowe said:

Is the Rostra cruise similar to the Audiovox CCS-100?...On the Gen I bikes, dip switch #7 "on" On some of the Gen II bikes, dip switch #7 "off"

Click to expand...

No, the Rostra is not like the AV CCS-100 and switch 7 doesn't apply.

All Gens FJRs should have dip switch 7 off, it was an oversight by the original install instructions to have switch 7 turned on. In the ON position it tells the cruise control CPU that the ignition system is an electrically messy breaker point system, in the OFF position it tells the cruise CPU that the ignition system is controlled by an electrically clean ECU signal. The cruise CPU changes the way it processes the two different type signals.

There is something different in the Gen II coil signal that the CCS-100 didn't like with switch 7 ON. If a Gen I cruise is working with switch 7 ON, relax, you don't have to do anything. If a Gen II has switch 7 ON, it really should be turned OFF to prevent unexpected shut-downs.

it depends on the voltage requirements of the coil. One can use 12v DC to draw in a coil for a 1200 amp AC contactor. Lots of

applications use 24V AC or 120V AC for control purposes to control voltages of 100K or more. The coil voltage is independent

of the system voltage, hell use 5 millivolts to control 10,000,000 volts if you want.