If I recall correctly from my electrical engineering courses forty years ago, "current inrush" is an important consideration for AC-powered solenoids but has no significance for DC-powered solenoids.
Actually, it's the same effect. According to this link from the Argonne National Laboratory which explains it pretty simply.
I also remember from my days as an Electrical Operator on submarines that anytime we started a motor, be it DC or AC, there was always a large initial starting surge until the magnetic field of the stator (which is a fancy name for a coil) built up to counteract it (that's the concept of counter EMF or counter electromotive force). The surge is as much as 7 to 10 times the running current of the motor. Considering the size of some of the motors on a submarine, some were 200 to 250 KW which works out to be a running current of over 400 amps with a starting surge of over 2400 amps AC (and we aint talking 120VAC either). I remember seeing the ammeters for our Turbine Generators pegging which is a pretty frightening experience until you get used to it
Greg
06 Aerolite Cub 236 ordered the way the DW wanted it
06 Chevy 2500HD CC SWB 4x4, LT3, LBZ, Duramax/Allison, Equalizer & Prodigy
06 Golf TDI (we are a 'Diesel Only' family)
jody h wrote: It might not on a single axle but a double or triple axle if one tire goes in a hole or dip then the chain would keep the wheel from traveling down and put more weight on the next tire and axle. Does this make since or am i thinking wrong here?
I re-installed the brake wiring on my previous 19ft 2 x axle system years ago. Also coverted it from a single run "T" wiring system to a Star wiring system. Also installed chains at each hub to support its 10 Guage wiring as well. For a picture, surf: - Click Here 1 - and - Click Here 2 -
Note: I ran this upgraded Brake configuraiton for years without any braking trouble. Actually, I found its braking system worked much better. Especially with upgraded 10 Guage wiring and the use Star Wire configuration.
If wondering, these wheel hub area "support chains" do NOT support the weight of the axle, or its attached leaf spring system. They are installed loose. Again, see the above link to confirm these chains are loose. To create proper length chain, jack up the frame / box chassis until no weight is on the leaf spring system. In other words, "NO LOAD" on its suspension system. Add 1 more inch of chain slack (for outward leaf spring flex - which is rare) and "that's the proper chain length". The wire loom is only twist tied to the outside of this chain. When a big stick, or old tire chunk, or large rock (or other road junk) goes flying behind the wheel hub area, this "wire proteciton chain" deflects the road junk. Without a chain, the unprotected brake wiring would be ripped out. As stated, the chain is loose - for movement. Same applies to both single axle and double axle trailers.
Edit: If chain isn't a good idea for some, they can also use a short steel cable. Something that is "much stronger" then 12V 10 Guarge wiring. Thus, when road junk hits this cable bundle, the steel cable will protect it. For deflecting road junk in this area, a thin Steel cable works just as good as a small chain.
Hope this other picture helps give a better visual as well...
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* This post was
edited 09/07/07 02:51pm by spike99 *
I'm curious how many people have actually had "Road Junk" take out a brake wire? seems like the leaf spring hangers etc would keep some of it protected. With the Star wiring, you are no longer risking taking out all of the brakes, just that on wheel.
I just re-wired my 06 prowler to the star pattern using pvc conduit and 12 ga wire. Just got back from a 400 miles trip with lots of hills, and did not see the short or overload error on the prodigy AT ALL. Prior to this, I couldn't bring it home the 10 miles from the storage lot with out seeing the error at least a couple times...
One of the first things taught in a Basic Electronics class is how a coil (inductor) opposes a change in current flow. This characteristic by default inhibits an "in-rush" of current in a DC circuit, making it ramp up to it's max over a period of time instead of jumping up all at once.
For a simple explanation, with pictures, of this principle, click here.
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edited 09/10/07 12:39am by JConatser *
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LIKE2BUILD wrote: I think I may install a bus bar like the one below to make my connections. In fact, I may run separate grounds to each brake just to ensure everything is getting maximum current and minimum resistance.
Well, I finally got it done. I had two spools (one red, one black) of 10ga wire, so I just used that instead of buying new wire. I know we had discussed on here (at length ) what the proper wire size should be. I was going to use 12ga, since technically that should be sufficient, but since I had the 10ga on hand there was no use in buying something else.
I had originally intended to use a bus bar like the one pictured above. However, I never got around to getting that one ordered and decided to buy something local. I went to my CarQuest store and they ordered a Cole Hersee brass terminal bus bar. I got two of them so one feeds the brake + and the other is for all the neutral lines (battery, frame, vehicle, individual GND to each wheel, and lights). The nice thing about this one was the 1/4" lugs that allowed to connect the frame GND and battery GND (both #8 wire) to those heavy connections and leave the screws on the terminal for all others.
We're going out this weekend, so I'll get a chance to find out if the new wiring scheme has improved my braking performance. However, given the amount of corrosion I found inside the wire nuts by the wheels, I'm guessing it will be much better. I'll post back on Monday how it goes.
BTW, here's a picture of the terminal block. They were just about $12 (US) each.
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edited 10/26/07 01:15pm by LIKE2BUILD *
BurbMan wrote: Where did you mount the bus bar? I would think that's corrosion (and resistance) waiting to happen if not enclosed somehow....
There is a small compartment inside the trailer under the front bed. So, there is no weather exposure for the bus bar. Otherwise, I would have had to get something in a weatherproof box.
Towing update:
The problem wasn't the wiring to the brakes We didn't get very far down the road before the problem occurred. One thing is slightly different though. Previously I would get an SH error message and then OL, but this time I only saw the OL. I would depress the brake pedal and see up to 2.0 or 2.5 on the display and then see OL and the brakes would be gone.
Tekonsha tech support says this about the OL error:
Quote: Q.) The Display shows "OL".A.) The Prodigy® detects an overload caused by a short to ground on the brake wire (Blue wire). The Prodigy has to have a complete circuit from the control to the brake magnets to the ground and has to have the proper resistance. Possible Causes:
· Short to ground on the brake circuit wire.
· Trailer has electric over hydraulic brakes.
· Faulty control.
So, either I have 1 or more bad magnets, or the Prodigy controller itself is faulty. I've towed my friends tandem utility trailer and have never seen any errors pulling that. However, it only has brakes on 1 axle so I'm wondering the controller is only showing it's problem when there is a demand for 4 brakes versus 2?
This week I'll test the magnets for a short between the hot and neutral wires. If there is none, I'm going to talk to Tekonsha about getting a replacement controller. When I bought this 2 years ago I thought I was getting a version 2.6, but recently I looked at the original box and on the bottom is a sticker that reads v2.4 so I'm really beginning to wonder if there might be some problem with this version of the firmware or hardware in the controller.
LIKE2BUILD wrote: Towing update:
The problem wasn't the wiring to the brakes We didn't get very far down the road before the problem occurred. One thing is slightly different though. Previously I would get an SH error message and then OL, but this time I only saw the OL. I would depress the brake pedal and see up to 2.0 or 2.5 on the display and then see OL and the brakes would be gone.
Tekonsha tech support says this about the OL error:
Quote: Q.) The Display shows "OL".A.) The Prodigy® detects an overload caused by a short to ground on the brake wire (Blue wire). The Prodigy has to have a complete circuit from the control to the brake magnets to the ground and has to have the proper resistance. Possible Causes:
· Short to ground on the brake circuit wire.
· Trailer has electric over hydraulic brakes.
· Faulty control.
So, either I have 1 or more bad magnets, or the Prodigy controller itself is faulty. I've towed my friends tandem utility trailer and have never seen any errors pulling that. However, it only has brakes on 1 axle so I'm wondering the controller is only showing it's problem when there is a demand for 4 brakes versus 2?
This week I'll test the magnets for a short between the hot and neutral wires. If there is none, I'm going to talk to Tekonsha about getting a replacement controller. When I bought this 2 years ago I thought I was getting a version 2.6, but recently I looked at the original box and on the bottom is a sticker that reads v2.4 so I'm really beginning to wonder if there might be some problem with this version of the firmware or hardware in the controller.
KJ
If you have a CW near you, just take your Prodigy into them, and they will quickly test it for you by hooking it up to a tester. I had it done to mine; took them all of 10 seconds to tell me it was faulty. 5 minutes later I walked out of there with a brand new one, most recent version of course, free of charge (via Tekonsha's lifetime warranty)...
________________________________
2005 Ford F150 SuperCrew, 5.4L, 3.73 LS, 2wd
2007 Adirondack 31bh-dsl
Prodigy Brake Controller, 1200lbs Reese Trunnion HP Dual Cam
Owner/Member - Silent Valley Club ~ Banning, Ca
BenK wrote: This is a solenoid, therefore 'inrush' an issue if the gauge too small.
This has to do with magnetizing the solenoid (the puck on the drum flange).
AC solenoids have inrush. DC solenoids do not.
The current in a AC solenoid is determined by the complex impedance. The inductive portion of the impedance will vary with the inductance of the coil - which will increase when they pull in. Before they pull in, the inductance will be low, causing an inrush.
When DC is applied, the current is only determined by resistance. Pulled in or not, the DC resistance is the same. The current will drop a little as the coil heats, but nothing like the inrush on a AC solenoid.
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) what the proper wire size should be. I was going to use 12ga, since technically that should be sufficient, but since I had the 10ga on hand there was no use in buying something else.
We didn't get very far down the road before the problem occurred. One thing is slightly different though. Previously I would get an SH error message and then OL, but this time I only saw the OL. I would depress the brake pedal and see up to 2.0 or 2.5 on the display and then see OL and the brakes would be gone.
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