• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help PLEASE

Status
Not open for further replies.

FlatButt

New Member
Hi, I have a 12 volt dc circuit that has two (2) separate 12 volt positive inputs and two (2) separate 12 volt negatives. Both positive and both negative inputs are from the same 12 volt vehicle source (circuit 1 is switched via my vans ignition), (circuit 2 is manually switched via a toggle switch) and both are used to feed a 12v to 5v USB converter at 1.5 amps which powers an Xplore C+1 Dash Cam.

I need ALL of the feeds (the 2 Pos + the 2 Neg) to be isolated from each other so that one circuit (supply) does not feed the other at ANY time.

Should I put Diode protection on ALL four leads? (2 positive and 2 negative)

The normal circuit (1) is powered via the the ignition and is for my Dash Cam when the van is in motion.

The second circuit (2) is powered from the fuse box (currently switched on/off by toggle) which is going to be replaced with a remote controlled switch, so I do not need to enter the van to switch the toggle on/off for downloading the recorded images.

The Camera uses WiFi to download the recordings to cellphone and or tablet via an Android App and decode the recordings and GPS data.

Which can not be done on a PC as the camera operates on its own specialised Android App and is painfully slow to download and convert each 3 minute video recording. In order to retain the GPS data the Android App must be used. Removing the mini SD card and transferring the video to PC does not give the GPS data.

I will be replacing the toggle switch with a remote controlled switch, which I have. But it ONLY switches the NEGATIVE circuit leaving the Positive uncontrolled (hot) and this is my concern with back feed.

I WILL be using diode protection to stop the 12 volt positive feeding back into the ignition and vice versa into the remote switch via the fuse box. I feel that I should also be using diode protection on both of the negative sides as an extra precaution.

Should I use diode protection on both the positive and the negative leads (of which there are 2 of each) or just the 2 positive inputs?

To date I have spent in excess of $120,000 New Zealand dollars in buying this van and having it professionally converted so I can drive from my wheelchair and I can not afford to blow any of the multitude of computers up that control its many standard and additional mobility related functions.

I do not need any additional hardware as I have everything that is needed and a working circuit that is manually toggled on/off but is un protected from current/voltage feed back.

All I need is advice on using Diode Protection on both Positive and Negative inputs. Your thoughts and views please.

Many Thanks Ray.
 
Last edited:

FlatButt

New Member
Hi cowboybob and thanks for the reply.

I already have ALL the hardware required for my project.

What I need to know is should I use SHOTTKY Diodes on both positive and negative leads of which there are 2 of each for 2 different power sources into a single 5v USB converter with 2 USB outputs.

Neither circuit can have any feedback from the other.

I played around this afternoon and have put SHOTTKY Diodes on both positive leads, but as the remote switch controls only the Negative 12 volts should I also put SHOTTKY Diodes in both of the Negative inputs.?

All of the under the hood wiring is in place and I just need to connect it up via the single channel remote switch.

I just don't want any current feedback as these damn vans have computers for everything..
 

Les Jones

Well-Known Member
Most Helpful Member
Hi Ray,
I am trying to get a clear picture in my mind of what you are trying to do. My understanding is that the 12 V to 5 volt converter is to be powered when you are in the van from the van battery via the ignition switch and the 5 volts supplies both the dash camera and your cell phone. I am not clear about the second 12 volts supply. Is it a second 12 volt battery in the van that is only used to power the 12 volt to 5 volt converter or is it an external power supply that you plug into the van ? Also you seem to be saying that the phone is still powered from the 12 V to 5 volt converter when you are not in the van. Is this correct or do you use the phone from outside the van to do the download ? By "single channel remote switch" do you mean a wireless romote control or just a toggle switch in the van ? Why can the switch only switch the negative ? If the second 12V power source is a battery in the van then how is it charged ?
Sorry to be just asking questions at this stage.

Les.
 

Diver300

Well-Known Member
Most Helpful Member
Cars and vans are all negative earth, so the car body is connected to the -ve of the battery all the time. The positive is switched for the accessory circuit. You need to check if the remote switch turns the +ve on and off, which I would hope it does. If so, you can connect the negative of your 12 - 5 V converter to any ground point. You then have two diodes, with the anode of one connected to the accessory +ve, the anode of the other connected to your remote switch output, and both cathodes connected to the +ve input of the 12 - 5 V converter.

If the remote switch turns the negative on and off, you are going to need a relay as well.

How much current does the dash cam take? How much current does the remote switch take? If they are not far different, you could just leave the dash cam powered all the time, and not use the remote switch. A lot of aftermarket car accessories take lots more current than the rest of the car when the car is shut down.
 

FlatButt

New Member
Hi Driver300.

The remote switch turns off the -ve only. Search E-Bay for DC-12v-10A-relay-1CH-wireless-RF-Remote-Control-Switch-Transmitter-Receiver and you will see the unit and its specs.
This is why I thought that diodes in all 4 leads (2 x +ve and 2 x -ve) would stop any flow back effect.

The camera uses 1 amp, the remote switch uses approximately 1 amp as well. The cellphone/tablet can be run on it's own internal battery therefore is not really part of the equation.

I don't want the dash camera powered all the time as the vehicle is only used occasionally to make hospital and doctors visits. My Wife takes care of every other need and she has her own car.

The main reason for wanting to do all of this is because getting in and out of the Van is a blardy nightmare due to my physical limitations and I can not reach up to the ignition switch from my wheelchair whilst being outside of the van (2015 Mercedes Sprinter converted for drive from wheelchair).

Cheers and thanks for your input and help

Ray
 
Last edited:

FlatButt

New Member
Hi Les.

Both +ve inputs and both -ve inputs are from the same in vehicle 12v battery. One +ve is switched via the ignition and the other is going to be switched via a single channel remote control when I am outside of the van.

The issue is that each +ve (2x) and -ve (2x) feed the same 12v to 5v converter from the same vehicle battery and must be electrically isolated from the other. lets take a +ve and a -ve and call them supply point 1, This supply point is via the ignition switch. The other +ve and -ve we will call supply point 2, this supply is direct from the fuse box in the van via the remote switch. Supply point 1 must not be able to feed back into supply point 2 and vice versa.

Currently I have a manually operated (Toggle Switch) which is used to switch the +ve off and on from outside of the van. I want to replace the Toggle with a remote control so I don't have to go outside in inclement weather turn it on and go back inside, download the recordings, go outside, switch the toggle off etc.

In the current circuit I have there is no protection from feed back except for having to remember to make sure the Toggle switch is turned off before turning the ignition switch on as the switching is done on the +ve.

The remote controlled switch, (search E-bay for DC-12v-10A-relay-1CH-wireless-RF-Remote-Control-Switch-Transmitter-Receiver this will give you more detail) switches only the -ve (either normally open, or normally closed (in my case normally closed would be the option I would use)) with the +ve being an un-switched 12v supply.

Therefore I would put a Shottky Diode in both +ve feeds and feel that I should also put Shottky Diodes in both -ve feeds as protection.

Hope this helps.

Ray.
 
Last edited:

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Concur. Confusing.

Is this correct or equlivelent?

You have a dual USB to cigarette lighter adapter.
One feed your cell and the other the dash cam when your in the vehicle.? ON in IGN position for the most part.
(Another possibility is the dash cam is on all of the time.)

So, when your in the house, you'd like to power up the dash cam with the remote and your phone is a separate entity.

==

Aside: Lighters can be on always or when the car is on. I have two cars wired one is wired one way and the other, the other.

I think we can re-think this and power the USB gizmo from either (IGN) or (ACC via remote)?

I'm just going to pick this http://www.ebay.com.au/itm/USB-Dual...-12V-Voltmeter-Cigarette-Socket-/322097349681 as an example. they make surface mount too. Single, dual and multiple. If you installed something like this, you can make it remote USB controlled or through the standard lighter (probably on when car is on).
 

FlatButt

New Member
Thanks for your reply.

I have ALL the hardware that I need and I already have a working (un-protected) circuit using a toggle switch as the second power input.

I will be changing this toggle switch for a remote controlled switch and I need diode protection on this circuit and via the usual ignition circuit so that one circuit will NOT back feed the other circuit.

The dash cam uses WiFi to download its images and GPS data to my cellphone and or Tablet. Cellphone / Tablet are self powered.

Dash cam needs 12v from ignition when I am driving and 12v from remote controlled circuit when I am out of the Van.

I can NOT leave the ignition switched to ACC and lock the doors whilst downloading, as the electronics in the van will NOT allow the doors to be locked with the key in the ignition. I do NOT want to have the dash cam on all of the time.

My current additional circuit is powered from the fuse box of the van and is controlled via a Toggle switch.

The remote controlled switch will take the place of the toggle and will do the same job. However the remote control only switches the Negative line NOT the positive. Therefore I WILL be placing a Diodes in the BOTH of positive lines to avoid feedback.

My question is "SHOULD I PLACE DIODE PROTECTION IN THE NEGATIVE LINES AS WELL?"

My Van is a 2015 Mercedes-Benz Sprinter Coach and it is full of dam computers to control everything. I also have had a hydraulic (electrically powered) wheelchair hoist installed, hand controls fitted, drivers side floor lowered to take my wheelchair and other modifications so I can drive it. My investment is this vehicle has gone over $120,000 New Zealand dollars and there is no way that I want to blow anything up.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Dash cam needs 12v from ignition when I am driving and 12v from remote controlled circuit when I am out of the Van.
This is really the key.

Your http://www.ebay.com/itm/DC-12v-10A-...765395?hash=item20fc2d1113:g:px8AAOSwstxVWbcA if that's correct is basically a relay.

So, the CONTACTS are ISOLATED.

The 12 V receiver would therefore have to powered all of the time from a BATT connection.

Your relay, would put the C (Common terminal) to the Dash Cam.
The (NC) or normally closed connection would go to the IGN side. Whatever is powered when the ignition is on. The NO or Normally open side would go to the BATT connection. You have to change your thinking a bit. The common terminal feeds the device, not the NO or NC terminal. It totally solves your isolation problem. No diodes necessary. If you would like, you can place a properly sized TVS (Transient voltage suppressor) at the dash cam side.

It used to easy finding those connections. These days, I have no idea.

Aside:
Since there is no feedback or two-way communication, what you might do is figure out a way to say activate the lights/horn or whatever. e.g 1 blink on, 2 blinks off.
A 2-hour timer or whatever would even be better.

You did a MUCH BETTER job describing the problem this time. I hope I did too.

FWIW, the car "used to" have an ON bus and an ACC bus. The ignition switch used to tie these together. Now it's difficult to determine if the engine is running. You almost have to use the CAN bus within the automobile. Flashing the tail lights like I suggested might also be nearly impossible.

Your image download may not be WIFI. Bluetooth makes more sense. That's immaterial.

Did you check the range? You may only have about 30 feet.
 

Diver300

Well-Known Member
Most Helpful Member
I agree with KeepItSimpleStupid, in that the modules from ebay have a relay output, and using the three terminals as described means than no diodes are needed. He didn't say that the negative of the dash cam converter needs to connect to negative permanently. Also the +ve and -ve supplies to the remote switch need to go to a permanent supply and to ground respectively. Those two are connected to the NO and to the -ve of the dash cam, so you still only need three connections from the car, ignition, permanent and ground.

I think that the remote switch will take about 10 mA when the output is not energised. Just running the relay when the output is energised will take more like 150 mA. Although the camera will take less than 1 A average, you should make sure that you turn off the camera or the drain will kill the car battery over a weekend.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
you still only need three connections from the car, ignition, permanent and ground.
Ignition = the circuits on when the engine is running or the ACC position. (Powers the dash cam when selected)
Permanent(= Circuits that are on all of the time; The battery. (powers the receiver; Powers the dash cam when selected)
Ground = the negative terminal of the battery. (permanently connected to dash cam and receiver all the time)

ACC is not the position of the ignition switch. It's the circuits activated by the ignition switch in ACC and ON positions. i.e. Radio

ON would include the turn signal circuit, back-up lamps etc.

The quiesient current of the receiver needs to be small.

As Diver and I both suggested, you need to somehow know the camera is off. If you can't connect, that might be enough.
 

FlatButt

New Member
Cheers and Thanks to KeepItSimpleStupid and Diver300. I have been trapped in a time warp for far too long. (old way of thinking) and yes the Remote is also a relay.

Thanks for clearing the junk from my mind. I guess that the accident that left me chairbound ahs also left part of me in the past.

Cheers and Thnaks Guys.
 

Les Jones

Well-Known Member
Most Helpful Member
None of the results that I looked at from a search that you suggested on ebay say that the unit could only switch the negative line. They all seem to have two connections for the twelve volt power supply and another three connections to the changeover contacts on the relay. If you look at ebay item number 152097088780 you will see a diagram of it switching the positive to a lamp. I have two of the four channel versions of these remotes. Their standby current is about 8 mA and when a relay is activated they take about 50 mA. The standby current of the single channel one will probably be the same as the 4 channel version. On my 4 channel units each relay provides a floating set of changeover contacts. If you provide a link to the ACTUAL item on ebay the I may be able to see why you think it can only switch the negative wire. If the 12 volt to 5 volt converter that you are using is the most common type you see sold in the £ shop chains (And elsewhere.) then these normally use a an MC34063 switching regulator chip (Or similar.) Which would work with th input voltage as low as 8 volts. This means that any normal diode such as a 1N4002 could be used instead of one of the more expensive schottky diodes.

EDIT.
I have just noticed some more replies have been posted while I was typing (Ind testing the current consumption of the 4 channel remote.) The point made about not knowing if the unit was left switched to the on position is a good one. If you used a 4 channel unit (Or probably a 2 channel one if they are available.) then they can be configured so that one button switches the relay on and another button switches it off. (In this mode only 2 of the 4 channels can be used.) I use one of the 4 channel units to switch on lights on our gate posts so We can see them better when reversing in at night. I have also added a timer so it switches off after 5 minutes if we forget to switch it off wth the button.

Les.
 
Last edited:

Les Jones

Well-Known Member
Most Helpful Member
In your link in post #15 the last picture shows that the relay contacts are floating. The positive input can be linked to the relay common with a blob of solder bridging the tracks neat the positive input.

Les.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
In your link in post #15 the last picture shows that the relay contacts are floating. The positive input can be linked to the relay common with a blob of solder bridging the tracks neat[sic near] the positive input.

Les.
It can. But why? Common needs to feed the Dash Cam. The dash cam needs power from two different sources. It's the common point.
 
Last edited:

Diver300

Well-Known Member
Most Helpful Member
In your application the Dash Cam needs to be switched from one feed to the other. That is not so usual. In most cases, there would be an output to be switched on, so connecting the common to +ve would work with the load connected to NO. In other cases there could be an output to be switched off, where common would be connected to +ve and the load connected to NC. So for nearly all uses, common can be connected to +ve, and the manufacturers have made that easy, but they realise that there are other uses that they won't have thought of so they let you remove the link and use the relay as you want.
 

FlatButt

New Member
OK, here is what I THINK I need to do. Please correct me if I am wrong (which is quite common) I have had to upload as a MS Word Doc as for some reason I could not upload as a JPG or PDF.
 

Attachments

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Sometimes the forum software is picky with extension case, but .pdf in lower case should have worked. It could be a case sensitivity. We know it happens in Linux. Basically you can't find the file to upload.

Looks good. You didn't label the top red wire. Should go to battery.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top