Hello guys,

I need help on how to reverse the polarity of an electronic signal.

lets say i have a negative triggered solenoid and then i have a device that should control the activation of the solenoid but this device only send (+) positive signal but since my solenoid needs (-) negative signal, i need to put something in between to reverse the polarity but wont affect the signal specs, only the polarity.

thanks in advance.

 

What are the input and output voltages and currents? Maybe you only need a BJT or MOSFET (with a catch diode).

 

im not sure yet what the IO voltages are. im a newbie with electronics tho.
but i think its a low voltage signal with about 2Amps of current.

basically im gonna use it for my car.


current setup:

ECU (-) --------> (-) MIVEC Solenoid



setup that i want

ECU (-) --- PI1 ---> (+) Apexi V-AFC (+) --- PI2 ---> (-) MIVEC Solenoid

PI1 = A polarity converter (negative to positive)
PI2 = A poarity converter (positive to negative)

 

Hi,
Do you really mean your existing solenoid pulse drive goes from 0volt to say +12V and you want to change it, so it goes from +12V to 0volt?

The reason I ask, usually on a car with a 12Vbty, either the car chassis is at 0V or +12V depending upon the model of the car.

If this what you mean lets know.

Eric

 

hi eric,

what i meant by PI1 is "polarity inverter 1" and PI2 is "polarity inverter 2".

Im not sure tho if my solenoid goes from 0V to 12V or vice versa. I only know that its a negative triggered device.

These are my stupid questions...forgive me for I am a newbie in electronics:

Kindly enlighten me...is it safe to say that negative signal has 0V and postive signal has +12V? Does polarity affects voltage?

thanks in advance.

cheers

 

hi,
Consider a device made for a car with a positive chassis, quiet often the device is bolted to the chassis. This would mean the controlling signal supply to the device would be from the high side of the battery, ie -12Volts and the chassis would be the return.

If you now tried to use this same device on a car with a negative chassis it would mean that the polarity to the device would be reversed. If its a solenoid it could have a suppression diode across the coil, which would have reversed polarity and blow it.

Even if the solenoid was chassis free, ie connection to the car metalwork and it had just two connecting wires, the solenioid diode, if one was fitted, would be designed to have the required correct polarity.

If the solenoid is controlled by the car's EMU then there is also a possibilty that it may contain other semiconductor devices.

Do you have any more details of this solenoid.

Eric

 

Hi Eric,

thanks for your reply.

the solenoid is like the Honda Vtec solenoid which is a soleniod that is used to activate the Hi-Cam profile of the camshaft of a car's engine. The only difference is that the Honda's Vtec solenoid is triggered by a positive signal while Mitsubishi's Mivec is negative-triggered.

 

what car out there has the positive side of the battery tied to the chassis? please let me know, as i never want to go near it.

this just sounds as though the solenoid he has is already tied to +12V on one side and to make it actuate he just needs to pull the "control" end to ground.

if this is a signal from the mcu and you don't know the min/max ratings on the voltage and current of the signal, then i would suggest buffering it and then use the buffered signal to drive the gate of an n-fet, source of which is tied to ground, drain of which is tied to the "control" end of the solenoid.

 

I think the last holdouts to converting to negative ground systems in vehicles were the British models up to 1967 including such cars as MG, Jaguar, Triumph, Austin and others. Coorespondingly or coincidentally, older British cars have a reputation for having extremely unreliable electrics so you would be doing yourself a favor by not wanting to go near them.

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RadioRon

 

As long as they had dynamos and not alternators, they were VERY easy to convert to negative earth though.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Fuel injectors usually have +12 V. to them at all times. They are grounded to operate because MOSFETs do it so well.

While we are on the subject of positive ground…
ELECTRICAL THEORY OF SMOKE...BY JOSEPH LUCAS
Dark Suckers
Ban Dihydrogen Monoxide!

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C:\WHUT ?
Beware the asterisk *

 

The OP is confusing reversing polarity with sinking or sourcing control of a device, plain and simple. All the off topic responses about some older cars using positive ground Vs negative ground system does not help the poster understand what help he needs to solve his problem.

Simply put if a device has one side hardwired to circuit common then it can only be activated by something that sources a current. If it has one side hardwired to the working voltage (positive or negative voltage relative to circuit common) the the device can only be activated by something that sinks current to circuit common.


Lefty

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Measurement changes behavior

 

I think you've sussed it there.

In car terms (well for the majority of them) a negative trigger normally means the trigger wire is grounded when active. A positive trigger normally means the wire is brought live when active. When there is no trigger then the wires can be considered floating.

 

You British with your wierd words What the heck does "sussed it" mean

Lefty

__________________
Measurement changes behavior

 

sussed = worked it out lol