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Topic: Problem using a voltage divider to input a voltage to a low impedance line (Read 3 times) previous topic - next topic

jackrae

You seem to be making hard work out of this project.
You can drive an open collector transistor or FET from the arduino. Your 50ohms load is connected between your 12 volt supply rail and the collector of the transistor.

MarkT



What is the load?


I need to send a signal of between 0 and 12 Volt to an electric-over-hydraulic trailer brake.


If there's a datasheet for the device it would be really re-assuring to see it - I don't know how such a thing works and what sort of frequencies of PWM are suitable.

Also automotive devices often are permanently connected to the chassis/ground and can only be switched on the high-side - if this is so you'll need a PNP or p-channel device to switch and some kind of level-shifting circuit to control this from the Arduino.
[ I won't respond to messages, use the forum please ]

Daanii


You seem to be making hard work out of this project.


I certainly am making hard work out of this project, aren't I. Two or three times, I thought I had it solved, only to have it not work and have to go back to the drawing board.


You can drive an open collector transistor or FET from the arduino. Your 50ohms load is connected between your 12 volt supply rail and the collector of the transistor.


I can't do that because I only have one wire that goes to my "load." Not two.


If there's a datasheet for the device it would be really re-assuring to see it - I don't know how such a thing works and what sort of frequencies of PWM are suitable.



There is no datasheet. There is a manual: www.championtrailers.com/BRAKERITEMANUAL.pdf The wiring diagram is on page 19 of the manual. I called up Titan and they said that PWM will work fine, at frequencies from 200 Hertz to 20 kilohertz.


Also automotive devices often are permanently connected to the chassis/ground and can only be switched on the high-side - if this is so you'll need a PNP or p-channel device to switch and some kind of level-shifting circuit to control this from the Arduino.


I think that is the situation here. The device is wired to ground and I just have one signal wire that I need to work with. I need to source a signal between 0 Volts and 12 Volts using the Arduino, at currents up to about 240 milliamps. At least that is what I have come up with so far.

Grumpy_Mike

Quote
I can't do that because I only have one wire that goes to my "load." Not two.

No you always have two wires to connect to the load otherwise you can't get any current to flow.
Your other "hidden" wire is either the ground or the +ve power supply.
What do you need to do wit this wire to turn it on. If it is supply +ve then the ground is your other control wire.

Daanii


Quote
I can't do that because I only have one wire that goes to my "load." Not two.

No you always have two wires to connect to the load otherwise you can't get any current to flow.
Your other "hidden" wire is either the ground or the +ve power supply.
What do you need to do wit this wire to turn it on. If it is supply +ve then the ground is your other control wire.


You're right, of course. The "hidden" wire in my case is the ground. What I meant, and should have said, is that I cannot connect my load in series between the 12 Volt power supply and the collector of the transistor because the ground wire must be connected directly to the battery's negative terminal. I cannot control the ground wire.

My device has three wires going into it. (Actually, five wires, but two of them are not important here.) One wire is 12 Volt power, and needs to be connected to the battery's positive terminal. One wire is ground, and needs to be connected to the battery's negative terminal. The third wire is the signal wire, which needs to vary between 0 Volts and 12 Volts.

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