I need a recommendation on a diode please.

Thread Starter

davidbanks

Joined Oct 15, 2021
7
Hi, I hope you're having a good day.
I need a diode to handle 13.8V at 7 Amps, It's for a Redarc electric brake controller in a car to apply the brakes on the caravan which (as a feature) enables you to apply the brakes manually on the caravan via a variable resistor mounted on the dash. When this is turned it sends voltage to the Trailer Plug Brake Light Wire which is also connected to the car brakes, (and also applies the caravan brakes on a separate wire), so when the brakes are applied via the variable resistor it would send unwanted voltage back to the car via the normal car brakes wire, this is also connected to the cars Can Bus System which controls the adaptive cruise control, hill descent control and other electronic circuits, so I need a diode to stop that, I was thinking of the Diode MBR735 Schottky 35V 7A TO-220-2 https://www.jaycar.com.au/diode-mbr735-schottky-35v-7a-to-220-2/p/ZR1029 but am concerned about the reverse leakage current, I have no idea if it would be a problem or not to the car. The voltage drop of a silicon diode shouldn't be a major problem as it's only for brake lights, but I can't find one to handle 7+Amps, so I thought of using a them in parallel but this would again increase reverse leakage I believe? Redarc do make an "Encapsulated Protection Device" for $61 which is a bit steep being just a diode.
Suggestions please.
Thanks for your time.
 

Ramussons

Joined May 3, 2013
1,417
What is critical here in the Current Carrying Capacity.
Googling for a "10 Amp"diode gave a whole list.
Schottky, Power, .....
Maybe this will do. "10A10 Rectifier Diode"
 

LowQCab

Joined Nov 6, 2012
4,218
Ask the Technical-Representative from Redarc about any compatibility issues with your particular vehicle.

Do not assume anything,
the high likelihood of your making a poor decision could easily cause loss of Life,
and would certainly void any warranties supported by Redarc.
.
.
.
 

MisterBill2

Joined Jan 23, 2018
19,055
(Words removed)
But after revisiting the #1 post, my question is about any feedback from the electric brake feed, which should not have anything to do with the brake light circuit control.
The caravan brake lights should not be wired in parallel withthe tow vehicle brake lights on a modern vehicle with a computer module to control the lights.
The caravan brake lights are a much lower current than the brake magnets, and at least in my installation are totally separate from the brake light operation circuit.
The trailer brake lights have a separate power feed, independent from the brake operating controller, as well. The only connection relative to the trailer brake lights is a pilot signal that drives a transistor to feed 12 volts from the vehicle battery source to the brake lights. This is because the electronic brake light control system for the vehicle would detect the greater current from the additional caravan brake lights and signal a system fault warning. I did get that module installed, and after it failed from the dealer installation I wired it in correctly, no more problems.

So you need to read and understand the operation of the brake controller relative to the caravan brake lights.There should not be any feedback possible to the vehicle rear brake lights control.
If there is feedback, I suggest return the package and get one that does not have any feedback..
 
Last edited:

Thread Starter

davidbanks

Joined Oct 15, 2021
7
Thank you for your comment Ramussons, and yes true there are many, I can't believe I didn't Google :\ I did search the major component stores nearby to no avail. I really need to know what diode would be best for the situation.
 

Thread Starter

davidbanks

Joined Oct 15, 2021
7
Thank you for your reply MisterBill2. Yes the brake activation wire and the brake light are completely separate. I am only talking about the brake light wire. Please see the images attached to see what I am doing,

canbus.jpgbrake light.jpgEncapsulatedProtectionDevice.png
 

MisterBill2

Joined Jan 23, 2018
19,055
The logic of the manufacturer's explanation is a bit foggy as I see it.
I am presuming that this is a new installation of a towing brake system in a vehicle that previously had none installed. Where will there be a "trailer brake light wire from vehicle" as mentioned in that explanation??
I had guessed that, as in my vehicle, I was taking the "brake light signal"from the existing circuit that feeds the vehicle brake/turn light assembly, not an independent circuit from the vehicle computer.
One serious caution is that the circuit shown would be powering the caravan brake/turn lights from the vehicle light power, not just using the vehicle light signal as a control for the towed vehicle lights. At least it looks that way.
 

Thread Starter

davidbanks

Joined Oct 15, 2021
7
Hi MisterBill2, yes this is a new towing electric braking installation for our vehicle which previously had none.

The trailer brake light wire from the vehicle is the same trailer brake light wire that currently goes to the pin 6 of the trailer plug, it is just having a diode put in it in series, to stop the voltage that is delivered by the Tow-Pro Elite Brake Signal Wire, (the words Brake Signal in this case merely represents the Brake Light), and the only time this Tow-Pro Elite Brake Signal Wire has voltage is when the variable resister on the dash is turned to manually apply trailer brakes, this is useful for off-road driving.

I am not sure where the pin 6 (brake light pin) of the trailer plug is currently sourcing its voltage from, when I said it is connected to the CAN System I was merely stating what the image 4.2.4 above states about vehicles with a CAN System. The towbar and current trailer plug were "professionally installed" so the source of the power for the brake lights (and other lights) would be coming from where it should be coming from.

Long story short, I was trying to save a bit of money with a simple(?) question about which diode to use, but I am biting the bullet and just going to buy the massively overpriced $61 Encapsulated diode. Having not got a simple answer to which diode to use makes it not worth the risk of possible damage that may be caused to the vehicle.

Thank you for your input.
 

MisterBill2

Joined Jan 23, 2018
19,055
Hi MisterBill2, yes this is a new towing electric braking installation for our vehicle which previously had none.

The trailer brake light wire from the vehicle is the same trailer brake light wire that currently goes to the pin 6 of the trailer plug, it is just having a diode put in it in series, to stop the voltage that is delivered by the Tow-Pro Elite Brake Signal Wire, (the words Brake Signal in this case merely represents the Brake Light), and the only time this Tow-Pro Elite Brake Signal Wire has voltage is when the variable resister on the dash is turned to manually apply trailer brakes, this is useful for off-road driving.

I am not sure where the pin 6 (brake light pin) of the trailer plug is currently sourcing its voltage from, when I said it is connected to the CAN System I was merely stating what the image 4.2.4 above states about vehicles with a CAN System. The towbar and current trailer plug were "professionally installed" so the source of the power for the brake lights (and other lights) would be coming from where it should be coming from.

Long story short, I was trying to save a bit of money with a simple(?) question about which diode to use, but I am biting the bullet and just going to buy the massively overpriced $61 Encapsulated diode. Having not got a simple answer to which diode to use makes it not worth the risk of possible damage that may be caused to the vehicle.

Thank you for your input.
The first "professionally Installed trailer light installation I ever had, from the trailer dealer (Caravan Dealer) was so poor that the wires burned thru the insulation where the harness rested on the exhaust pipe, that I do not consider "professionally installed" to mean done correctly done. The second "professionally installed" installation, done as part of the hitch installation, took the +12 volt supply to the stop/turn lights control module from a low-power circuit that was not always powered. So again, I do not consider "professionally installed" to mean done correctly done. I had to rewire that feed to a fused battery connection myself.
My point being that just because somebody charges for the work does not mean they did it even close to correctly.
 

Thread Starter

davidbanks

Joined Oct 15, 2021
7
Totally agree, I often find professionally installed means done without care, which is why I did mine myself. I bought the $61 diode and still cannot open the unit to see what diode is in it as it is sealed, but it does work, so on to my next project. Thanks for your time and input!
 

Thread Starter

davidbanks

Joined Oct 15, 2021
7
*I did the upgrading to 12 pin from 7 pin myself, I have checked the routing of the "Professionally installed" 7 pin wiring to ensure that it is away from heat and secured, in checking that, I did find they had bent 4 of the factory supplied clip mountings in order to fit the towbar that they hadn't bent back to enable putting the clips back in. It was done in a very professionally careless manner.
 
Top