There are no standards for wall warts other than the typical NEC Class 2 designation which pertains only to fire and shock hazards. Otherwise, it's a wild and woolly world out there.
This thread caught my attention because, just a few days ago, I had the occasion to come up with a 9VDC supply for a device after the original wall wart was lost. I dug into my box of wall warts and found a 9VDC unit with the wrong plug on the end. I found another different-voltage wart with the right size plug. Both were marked with the center pin positive. I cut the plug off and spliced it in to the 9VDC adapter, connecting the white stripes together and the blacks together. Guess what happened! I damaged the device I was trying to get power to. I verified with a meter after the fact that the polarity was reversed.
Obviously, the wire markings are not standardized.
"The better grade of power supply the better the radio signal."
That makes sense. In the case of using the HP power brick, the very first thing I did was put the meter on it and verify voltage. Next, I put a load on it and checked for stability ... it was rock steady. I can't recommend it because it indeed was not designed for the TH tx, but what I can say is it's been in operation daily since back in April. It doesn't get hot, it doesn't falter (comes right back) even in power outages and glitches (we have them here). It seems to be taking very good care of the Talking House. It may be a wall wart of a type, but it's quite heavy, which would seem to indicate a hefty xfrmr.
Thanks to Neil for the correction about the no-ground wall wart. I guess I was thinking about possible polarizing error in that bad DVD player, which needs to be polarized, so it has the big blade. So how do these things ground? I.e., the negative side is the shield wire on the audio connections, which is the DC return path, and is also the chassis ground on some of my gear with internal PS'.
Ken,
I think there is some confusion about "grounds" because I suspect you and I are referring to different things. In my post earlier I used ground to refer to the power line ground and perhaps you are referring to circuit ground.
Here's a brief primer on the topic. The power line ground is a protective connection which is not intended to carry power current. The power line ground is connected to a single point, usually a ground stake, at the point of power entry into a building. One of the conductors which carries current, the "neutral", is connected to the power ground at this point. The other conductor, the "line", is at 120 volts above the neutral and ground potential. The power current flows through the line, through the load which is connected between the line and neutral, and back through the neutral. A wall wart transformer primary is connected from line to neutral but the secondary which provides the output is isolated from the line, neutral, and ground. There are exceptions where the output may be connected to the power ground through the third round pin but these are rare.
Circuit ground refers to a common reference connection point in a device or system. This ground is not the same as the power line ground though it can be connected to the power line ground. When this is done the connection should be made at one physical point to avoid the ground loops referenced in other posts. Circuit ground is usually the negative side of a DC supply or the common reference connection for audio and other signals. Current from a wall wart or other supply does flow from the "hot" or "B+" lead back to circuit ground but not through the power line ground. This, I think, is what you were referencing when you mentioned grounding while I was referring to power line ground.
I tried to keep this short but not so simple that it would be useless. Hope this helps.
Neil
Neil, I appreciate your willingness to provide technical explanations of such concepts as "grounding," which indeed can mean many different things in different conversations.
A college course on electricity or electronics would necessarily include a large segment devoted to the intricate details that describe the language of "ground."
I think there are even different circuit symbols, one of them resembling a pitchfork, the other sort of an arrow, representing different types of ground.
A gardener probably has the easiest time because I think they only have one kind of ground.
Carl,
I hope I didn't go off the deep end with this but I like to explain things. You are right about the upside down pitchfork with sideways bent prongs as a symbol.
Your gardening comment reminds me of a college prof. I knew who taught landscaping. He was very adamant that we do not plant things in "dirt" but rather in "soil". It was fun to needle him by saying dirt intentionally.
Maybe we should change the name of the power ground to "dirt ground" to avoid confusion with circuit or system ground. Let's see....dirt radials, dirt lead length, dirt waves, dirt stake, etc. What do you think?
Neil
Neil:
I think you were doing a play on words about my possibly "going off the deep end," as grounding runs deep sometimes.
Also, the idea of more distinctly naming the various things referred to as "ground" is probably what's needed. Sometimes the short-cuts we take in language can ruin any attempt to be exact.
Let's see, there's power ground, which in itself has more than one application; neutral ground; electric socket ground; lightning protection ground; circuit ground; radial ground... oh, heck, it's too big a job. Let me just lie down on the ground and watch clouds.
The Talking House power supplies that came with all of the units I purchased have a 3 prong wall wart.
The third wire "ground" pin connects directly to the negative side of the power connector that plugs into the Talking House transmitter.
It serves as the RF ground for the transmitter. The instructions caution that using an adapter to plug it into a 2 wire outlet will affect the range of the unit.
Other discussions here regarding the use of alternate power supplies (ungrounded wall wart) leaned towards using a separate ground from the transmitter to a suitable ground connection.
The third wire "ground" pin connects directly to the negative side of the power connector that plugs into the Talking House transmitter.
This is a good example of the proper use of a grounding connection for safety. In this case it contributes to performance.
Some of the wart type power supplies I've encountered used in commercial grade data processing equipment also used the third pin power ground for safety. For my uses which involve audio, video, and RF signals and devices I prefer to control the grounding independent of the plugs or power cords. For this reason it is good for me to use supplies which do not power ground their outputs. For safety and performance I permanently bond my radio and computer equipment to the power ground at one point.
I was once very involved in hospital electrical safety and the use of equipotential grounds was mandated. This is where a separate ground wire and terminals were available in operating rooms and intensive care units in which electrical devices were attached to this ground in addition to the conventional receptacle ground. I did studies which showed a very high failure incidence for the receptacle grounds in hospitals.
What seems so simple in theory is difficult in practice.
Neil
Potentially, grounds can also be in your coffee or tea. But with radio, let us not forget the venerable counterpoise. Made up of two words; Counter: indicating opposition or resistance and; Poise: balanced and stable, not embarrassed. If you have never used a counterpoise, now is your opportunity. The next time un-grounded equipment bites your lip with a small spark, remember your opposition to swearing (#@!*&^%!)* and remaining balanced and stable. This is not a technical explanation, but for the well seasoned Part 15 folks, its an opportunity to LOL. 😉
* -could this be the "dirty deep end"?
Marshall Johnson Sr. has indeed provided an early morning chuckle as he's carried the ground argument into more off shoots, and made the important reminder that with AM radio it's more about counter-poise than having a ground, unless this, and except that.
But WHAT IF lightning hits the radial counter-poisers and ignores the safety ground?
Is standing on top of the buried radials more dangerous than regular (earth) ground?
The subject has infinite depth.