Use of switchs that are "non rated" for DC

[Michael_T]

Okay, O'Godz of all Electric:

 

I am trying to get some additional utility from the "authority switch housing" by replacing the large BMW rocker switch with smaller (and, as a result, more) rocker switches. I got the idea from our "brethen" from the LT bulletin board. Here is an example: Phoenix Switch

 

In looking for switches that will fit, I have been told by manufacturers that I should not use of switchs that are "non rated" for DC current. I think that I understand that our rides, being run on battery power, are DC and that normal house current is AC.

 

But what is the down side to this situation -- are the manufacturers just CYA'ing or is there a real "danger" with me going to Radio Shack and picking up some minature rockers?

 

Michael

[GregB]

It simply means that the current handling capacity is different. I don't recall the factor but I'm sure it is less than 1.5x. So if you are going to run 10 amps DC through it, a 15 amp AC switch is fine.

[Aluminum_Butt]

The downside is that DC is tougher on switches when you open or close them. It has a higher tendency to arc than AC, and will wear out switches more quickly. The DC current rating on a DC rated switch is a fraction of the AC current rating on the same switch.

 

That said, I personally wouldn't worry about using non-DC rated switches, especially for low current stuff. You shouldn't push your driving lights through them (use a relay instead, anyway), but it's fine to run low current stuff like electronics. JHMO.

[smiller]

No problem, just de-rate the current carrying capacity of the switch a bit as suggested in the other responses (many switches will have two ratings stamped on them, one for AC and one for DC.) If you want to control any heavy loads (such as lighting) you should probably use a relay, so the switch itself won't matter much anyway.

[Michael_T]

Donkey shins for the input. On three another notes could someone comment on the following:

 

Should the relay be on the hot side or ground side of the light?

 

Should the fuse be on the hot side or ground side of the light?

 

 

Could someone comment on the wiring that is shown in the URL that I posted above. The writer indicates that the middle picture of the second row that the "red 14 guage wire" is the "main power supply" but that does not make sense to me as it seems that the same circuit is running through each switch. In the far left picture of the fourth row, he further indicates that the "blue wires" are for low wattage accent lights.

 

This seems backwards to me. I would think that the blue wires are the circuit for each relay to the farkle and the red wire powers the lights.

 

thx again, O'Godz of all Electic!

 

Michael

[ESokoloff]

Quote:

 

Could someone comment on the wiring that is shown in the URL that I posted above. The writer indicates that the middle picture of the second row that the "red 14 guage wire" is the "main power supply"....... the same circuit is running TO each switch.

 

 

 

Fixed it for you....

Do not confuse a series circuit with a parallel one.

Through each switch would indeed be series.

To each switch (as in the example in the image) is parallel.

Its much easier to run one adequate sized wire to all the switches then to run six separate ones.

Note that in doing so you should install a fuse after all the switch's or risk burnt wires.

 

Relays & switches are installed on the hot (+) side of the circuit.

Typically the fuse protects the wire & should be installed as close as possible to the beginning of it (in-line) if not before (fuse block).

 

 

The blue wires are on the switched side of the rocker switch's & eather power the accent lights directly (LED's are typically used for this & as they draw such low power, they do not require a relay) or will power a relay coil located in some other location.

 

 

I used two illuminated miniature rocker switches on my wife's bike for accent lights (LEDs) & to power the Moto light relay.

I think I got them from Auto Zone but a quick google search produced these..

I found that they were to bright so I installed a resister on in-line (series) with the ground terminal of the switch.

 

I don't know what they are rated for, but they are more than adequate for my low amperage purpose.

[ESokoloff]

Dang.......

Omitted the link to the switchs

[bimmers]

are they weather proofed would me my question. packing it full of dielectric grease may do the trick but the switchpart may still take in water/humdity.

h

[ESokoloff]

Very good point that I failed to cover.

They do not appear to be water proof & at their cost I'm sure they are not.

 

Due to the location I placed them (jammed between the space of the bar bracket & controls assembly) & the heat shrink tubing that incapsulates the sides & backs (also acts as a spacer to take up fit slop) I think they are adequately sheltered for this application.

I don't remember for sure, but my guess would be 20+k miles/4+ years ago.

I live in SoCal & don't over-wash my bikes but it has seen plenty of water with no problems to date.

[11101110]

the reason switches have higher amperage ratings for AC and lower DC is that AC turns off 120 times a second (the reason it is easier on contacts). Thus when using AC you don't need to put as much distance between the contacts as you do with DC. If you you have a 20 amp AC switch and try to run 20 amps DC through it you may end up with a sustained arc when you open the contacts. but at 12-14 volts I would be comfortable as long as I didn't exceed 2/3 of the AC current rating for 120VAC or less.

 

Fuse all lines as soon as they come off the battery.

Put all relays on the positive (hot) side.

 

Have you looked for marine grade switches?

[T__]

Okay, O'Godz of all Electric:

 

I am trying to get some additional utility from the "authority switch housing" by replacing the large BMW rocker switch with smaller (and, as a result, more) rocker switches. I got the idea from our "brethen" from the LT bulletin board. Here is an example: Phoenix Switch

 

In looking for switches that will fit, I have been told by manufacturers that I should not use of switchs that are "non rated" for DC current. I think that I understand that our rides, being run on battery power, are DC and that normal house current is AC.

 

But what is the down side to this situation -- are the manufacturers just CYA'ing or is there a real "danger" with me going to Radio Shack and picking up some minature rockers?

 

Michael

 

Michael, switch ratings are a long debated subject.. Especially when it comes to types of loads.. Resistive loads require a different set of values than inductive loads & AC voltage vs DC voltage plays into the equation.. Number of switch cycles also has to be figured in.. As the number of switch cycles goes up the so must the switch rating..

 

When they rate a switch they have no idea if it will be used on an inductive or resistive loads.. Inductive loads are very difficult to switch especially on DC..

 

Most all switches that are rated for AC loads also carry a DC rating (just might not be shown on the switch housing)..

 

Unless you are switching a strange inductive load a good rule of thumb is a switch able to operate an xx amp 125v AC load should also be able to switch an xx amp 12-14v DC load.. (note the voltage difference from AC to DC though)

 

The DC switching starts to become a problem as the voltage goes up (250 v DC is a real pain to deal with switch wise) ..

 

Twisty

[Dave_in_TX]

Quote:

Relays & switches are installed on the hot (+) side of the circuit.

 

Switches are typically installed on the hot side but don't need to be. In fact, some of the Japaneese bikes put the horn switch on the ground side rather than the hot side.

[Michael_T]

thanks for all the info, very informative. As for the use of marine switches, I have looked; however the size of the switch is the problem.

 

If you look at the URL that I included in my initial post, the switch case is holding 6 "over the counter" switches in place of the 2 BMW switches that the switch case was designed to accomodate. And then there is the cost.

 

Anyway, I am still puzzled by this paralell vs series thing in light of the pictures shown in the URL. Am I an idiot or, as shown, doesn't the red wire run "through" all the switches? How do you power individual item that come after the switch if there is only a common hot?

 

One of you Godz may have to draw this out for me. Keep in mind that I am the DYI guy who doesn't turn off the breaker box to change a light switch and, after I shocked the sh*t out of myself and "blew a fuse" when I pulled the switch from the gang box by reaching in on both sides of the switch, I went downstairs to reset the breaker BEFORE I finished the job.

 

anyway, my wife worries about me sometimes,.....

[ESokoloff]

Trust my Jedi friend, trust.

 

All you need to know is that the red wire is running TO all the switches, not through .

Look here for an example.

If still not clear, Google is your friend.

 

Note that the red wire goes TO the left tap of all 6 switches.

This is parallel.

 

If the red wire went to the first switch's left tabs & then out through . it's middle tab then went to the 2nd switches left tab & out it's mid tab And repeated this pattern on the remaining 4 switch, then it would be series.

 

Clear as mud yet

[T__]

thanks for all the info, very informative. As for the use of marine switches, I have looked; however the size of the switch is the problem.

 

If you look at the URL that I included in my initial post, the switch case is holding 6 "over the counter" switches in place of the 2 BMW switches that the switch case was designed to accomodate. And then there is the cost.

 

Anyway, I am still puzzled by this paralell vs series thing in light of the pictures shown in the URL. Am I an idiot or, as shown, doesn't the red wire run "through" all the switches? How do you power individual item that come after the switch if there is only a common hot?

 

One of you Godz may have to draw this out for me. Keep in mind that I am the DYI guy who doesn't turn off the breaker box to change a light switch and, after I shocked the sh*t out of myself and "blew a fuse" when I pulled the switch from the gang box by reaching in on both sides of the switch, I went downstairs to reset the breaker BEFORE I finished the job.

 

anyway, my wife worries about me sometimes,.....

 

Michael, without knowing what the pin-out of the switch looks like inside at the contact area this is mainly an educated guess..

 

It looks like the there is two banks of 3 switches (3 on each side).. The red wire is soldered to the supply side of the 6 switches.. The white/brn wire is soldered to all the R/H contacts of all 6 switches probably to power the internal switch lighting (the picture appears to show lit switches).. That would power & light all 6 switches.. It looks like there is no output soldered to the center terminals yet.. Those appear to be single throw switches so would not have need for 3 terminals on each switch if the 3rd terminal wasn’t for the switch lighting..

 

Twisty

[Michael_T]

THANK YOU, your explanation has triggered a "moment of clarity" for me:

 

The caption/explanation that the author of the URL gives for each picture is misleading, ie the red wire must be a low wattage input versus "main power supply" which I thought meant 12v DC and the blue wires are distributing the low wattage current to relays versus "low voltage for accent lighting" which I thought meant another input.

 

You guys correct me if I am wrong but I know "see" this as red wire low wattage into switch, white/black as common ground. Switch is "thrown"; current completed; LED goes on and low wattage goes to relay that allows 12vDC to power lights/farkle.

 

Pls don't tell me I am wrong; I've developed very low self esteem on this one.

 

Michael

 

PS: What is the "best" source of low wattage current or should I wire a resistor into an independent line from an aux fuse box?

 

Thx again all ye Godz of all Electric!

[ESokoloff]

My suggestion would be to get all your electrical goodies together & attend Phil's upcoming Tech Daze event for some hands on assistance/advice of your project

[RFW]

the reason switches have higher amperage ratings for AC and lower DC is that AC turns off 120 times a second (the reason it is easier on contacts). Thus when using AC you don't need to put as much distance between the contacts as you do with DC.

That is only partly correct.

 

The reason is several things. First, current does indeed cease briefly each 120th of a second, but this is not "easier on the contacts". In fact, what this does is tend to quench the arc that forms on opening the switch. A shorter duration arc means longer contact life.

 

The second reason is contact longevity. In a DC switch, the arc tends to cause much more erosion on the positive side of the switch (the contact that the electrons are flowing TO). With AC operation, when you average over many switch openings, the number of times the current happens to be flowing in one direction (instantaneously) as the switch is opened, is about the same as the numer of times it happens to be flowing the other way. The result is a lot less contact erosion.

[Michael_T]

My suggestion would be to get all your electrical goodies together & attend Phil's upcoming Tech Daze event for some hands on assistance/advice of your project

 

While a very good suggestion, time and availability are running thin.

 

Michael

[T__]

THANK YOU, your explanation has triggered a "moment of clarity" for me:

 

The caption/explanation that the author of the URL gives for each picture is misleading, ie the red wire must be a low wattage input versus "main power supply" which I thought meant 12v DC and the blue wires are distributing the low wattage current to relays versus "low voltage for accent lighting" which I thought meant another input.

 

You guys correct me if I am wrong but I know "see" this as red wire low wattage into switch, white/black as common ground. Switch is "thrown"; current completed; LED goes on and low wattage goes to relay that allows 12vDC to power lights/farkle.

 

Pls don't tell me I am wrong; I've developed very low self esteem on this one.

 

Michael

 

PS: What is the "best" source of low wattage current or should I wire a resistor into an independent line from an aux fuse box?

 

Thx again all ye Godz of all Electric!

 

Michael, in about every single throw switch I have seen the (power in) & (switched) terminal are not BOTH on the outside like shown.. The center terminal would usually be one of the switching terminals..

 

I’m not sure I buy a low wattage (low current) application.. Like I said above, without actually seeing the inside of the switches or at least a pin-out of the switches it is difficult to be sure exactly what you have but I still believe the LEFT & CENTER terminal are the power flow terminals & the R/H terminal is the switch’s light terminal.. The switches could still be used to power a power relay if that is what’s required (especially if ALL 6 switches are powered up from one input wire)..

 

 

 

I’m still just guessing here but I believe if the CENTER contact is powered (power to it) & the R/H terminal is grounded the switch light will be OFF until the switch is turned on, then the switch would light.. If the L/H terminal is powered (as shown in picture) & the R/H terminal is grounded the switch internal light(s) will be on as long as the red wire is powered up.. That would make the center terminals the place to connect the circuit loads..

 

It could all be reversed if relay grounding control was what was needed__ The white/brn wire could be powered & the Red wire grounded as that would light the switches & allow the center terminal to go to the low side of the relays for relay ground control..

 

It makes no sense to have the red wire running to all 6 switch terminals UNLESS it is the COMMON power feed.. It also makes no sense to have the brown/white wire running to all 6 R/H switch terminals unless that is for a common switch internal light ground..

 

As that switch bank is shown (at least it looks that way) as wired it would have common power to all 6 switches,, would have a common light ground to all 6 switches & the unused center terminals would be for individually switched loads attachment..

 

Easy enough to tell with an ohmmeter & a flip of the switch..

 

Twisty