12/24v converter question

I have a small 12/24 volt converter powering a CD player, a tach, and a recently installed Pyro guage. When the stereo is cranked, the pyro needle deflects 500 degrees...to the beat of the music! I assume I'm at the limit of power drawn from the converter...should I be running a filter of some sort...or a separate converter? Anyone have any recommendations of another converter that would run my stuff?

Yes, I think your guess is right, the converter is on it's limits. Especially if you have a lot of basses in the music. That draws a lot of amps.
Dunno what the pyro needs but I think buying/modifying a low cost 24/12V converter that delivers somthing like 1 or 2 amps can solve the problem.
Disconnect the pyro from the converter and connect to the 'dedicated' converter.
Or...buy a converter with a much higher rating and enjoy also more powerfull basses and use the old one fort the pyro and tach

Your existing converter may or may not be maxed.

The important specifications to look at are the voltage regulation and maximum power output of the converter. If the power draw is fluctuating, which it will invariably do with a stereo deck attached, the voltage may fluctuate as a function of the current if the converter circuitry is cheap and simple. The cheaper the converter, the more likely this is going to occur. As the old addage goes, you usually "get what you pay for." Test the voltage by using a multimeter on the output of the converter.

Another issue you may want to look into is the grounding of the Pyro. Current into any device must also flow full circle, i.e. electrons flow from negative to postive. Usually, the circuit is made by grounding the device to chassis. If the ground is poor and current is flowing through other devices nearby, a ground shift (measurable voltage at the device ground compared to battery ground) can be measured. This may affect the device (Pyro) in this case. I am not familiar with Pyros per se but I know a fair amount about ground shift and its effect on sensors.

Another possible cause is that the sensing element (I assume thermocouple?) of the Pyro is somehow grounded. Different grounds on the sensing element and meter may also cause havoc.

One further test to help isolate the problem, without buying another converter, would be to run the Pyro off a separate battery and see if you can eliminate the observations mentioned. Ensure, though, that the ground of the battery is attached to the ground of the chassis.

My guess is that the voltage fluctuates on the converter. As Ron R stated, either a better or separate converter would likely do the trick.

I have been using a converter from Samlex America (Vancouver, of all places), SDC23 (20A). [No affiliation]

Good luck, please post outcome.

Now I've discovered another problem, when I runa t night with the headlights on, the pyro deflects to zero. I can get the samlex converter locally here, in London Ontario, so I'm thinking of buying the small one just to run the pyro. I don't think I could be approaching the limits of my alternator could I? The headlight affect has me puzzled. The pyro right now is an auto meter, two wires going to the sensor, with the ground coming off the negative side of the converter. Everything ran fine, autometer tach, stereo, before the pyro install. Ideally I'd like to run one converter off the switched side of the 24v fuse block, for the tach and pyro, and the other direct 24v, so I don't lose memory on the cd player. Is it detrimental to run the converter constantly to provide the memory power?

Mszekely said:

Now I've discovered another problem, when I runa t night with the headlights on, the pyro deflects to zero. I can get the samlex converter locally here, in London Ontario, so I'm thinking of buying the small one just to run the pyro. I don't think I could be approaching the limits of my alternator could I? The headlight affect has me puzzled. The pyro right now is an auto meter, two wires going to the sensor, with the ground coming off the negative side of the converter. Everything ran fine, autometer tach, stereo, before the pyro install.

Click to expand...

Hmm, sounds like a grounding problem to me. Have you checked the mass connections from frame to engine? Take them apart, clean, put together and spray some kind of coating against corrosion over it ( clear wax, vaseline).
Don't forget to check ground between battery and frame.

Ideally I'd like to run one converter off the switched side of the 24v fuse block, for the tach and pyro, and the other direct 24v, so I don't lose memory on the cd player. Is it detrimental to run the converter constantly to provide the memory power?

Click to expand...

No, not detrimental but be aware that the converter (in total) draws a lot more than just needed to keep memory alive. So over time the battery can get drained. (a few weeks) Don't ask how I know.
To overcome this problem, I've build a very small 12V IC regulator (7812) to keep memory alive.
Nothing complicated just a connection between 24V + and ground and the output through a diode to the memorywire.
This solved my problem since my rig is not driven daily (sometimes even not weekly)

Mszekely said:

I don't think I could be approaching the limits of my alternator could I?

Click to expand...

Probably not. You could be though, or reaching the limits of the converter. Consider your alternator is likely 30amps@24V (might be 35amps). That is 60amps @12V. Add up all your loads, worst case scario...then total. That will let you know if you are reaching limits.

Also check your brushes...perhaps you alt is not putting out like it should.

And, as mentioned check your grounds from battery to frame, engine to frame, body to frame...and all battery connections.

Not all converters are equal. Some high end efficient ones draw no more when sitting then your mem preset, or such like minor draw, while others draw much more. Look to the heat sinks as a measure of efficiency. Contact your retailer or the manufacturer for specs if not on the info sheets. That will let you know what you need to figure. http://www.samlexamerica.com/customer_support/pdf/Converter_Industrial.pdf

hth's

gb

Check Pyro sensor element

OK. I looked up Auto Meter Pyros, and without knowing the model number but judging by a random selection of the Pyros, the sensor is a K-type thermocouple (as I suspected).

I suggest checking the grounds as already mentioned in a number of replies.

One further test is to check each of the 2 wires from the sensor (thermocouple) to the sheath (metal sheath of sensor) and/or ground with the sensor disconnected.

If you get a low resistance reading and you have bent the thermocouple severely whilst installing, you may have shorted the one of the sensing element wires to the sheath and I practically guarantee that the thermocouple will not work in such an environment. (The thermocouple wires are the same as used to make the junction at the end of the thermocouple. The wires run through a sheath that is filled with a ceramic powder that may or may not run continuously within the sheath to prevent the wires from shorting to the sheath)

The voltage produced by the thermocouple junction is in the 10's of millivolts. Any short to ground in the sensor and with the large currents flowing through the chassis, the signal voltage WILL be affected.

If the above diagnosis is correct, replace the sensor and all will be well.

Please post outcome of test. Thanks.

The thermocouple sheath was coiled inside the box, I had carefully uncoiled it and installed...All grounds have been checked and cleaned, I'll do the resistance testing tonight. The tach, pyro and cd player are all hooked up to the same power and ground wire off the 12v side of the converter. There has to be some grounding issue when I turn the headlights on, however when I do, only the pyro is affected.

If I disconnect the two sensor wires from the wire harness, I shouldn't have to remove the sensor right? I could look for a short from a sensor wire to the sheath or to the exhaust pipe...

Mszekely said:

The thermocouple sheath was coiled inside the box, I had carefully uncoiled it and installed...All grounds have been checked and cleaned, I'll do the resistance testing tonight. The tach, pyro and cd player are all hooked up to the same power and ground wire off the 12v side of the converter. There has to be some grounding issue when I turn the headlights on, however when I do, only the pyro is affected.

Click to expand...

Before you get into the headlight thing, read this so you understand your system. https://forum.ih8mud.com/showthread.php?t=68379

hth's

gb

I just read it, I'm running a nuclear reactor right now, and it's easier to do that than comprehend the 24/12 v tap system : )

I need a 24/12 volt converter. The most powerful unit Ive found is 80amps max 50 amps continuious. Has anyone found a more powerful unit?


TB

http://www.warningsystems.com.au/voltage_reducers.htm

I left the thermocouple (K type as you surmised) in situ, and disconnected it...both wires showed a dead short to the sheath...which made no sense to me, if it's shorted, I shouldn't get any reading. With the truck running, I did detect voltage coming from the two wires. With the CD player off, the pyro reads ok, when I turn the lights on it deflects to zero, and back to the previous reading instantly. With the stereo on, and headlights on, the needle goes to zero. I will try to hook up a second converter... I'm thinking the 24 v to the converter is being affected when the headlights come on, and that the converter is at it's limit when all electronics are running...I don't know what type converter or anything, no markings, installed by PO, but it is only the size of 1/2 a paperback, so it probably puts out 5 amps or less...

Thermocouple damaged?

Yup, based on what you say, it sounds like the thermocouple is damaged. Of this, I'm pretty sure.

If you get a voltage between the wires with the thermocouple disconnected, you are measuring the junction voltage referenced to vehicle ground (sheath ground). The reason you get a short to sheath for both wires is because the thermocouple wires are exactly that, wires. The dissimilar metal (Nickel-Chromium & Nickel-Aluminum)twisted junction generates the voltage as a function of temperature and cold, a resistance measurement with a normal multimeter will indicate only that you have a short, not on which wire (unless you dig a lot deeper).

I make the assumption that the Auto Meters Pyro requires a floating signal (i.e. no signal short to sheath). You could and should confirm this with them. If I am correct, the only way to resolve this issue is to purchase another thermocouple. If you do, please check for short between sensor wire and sheath before and after installation.

One final test you could consider before splashing out on a new thermocouple is: Remove the thermocouple from the block, reconnect to Pyro, heat with external source (read propane torch or similar mid heat source < 1380 oC) and run the conditions under which you observed the issue previously (CD player cranked, lights etc.) I bet the faulty Pyro readings cannot be repeated. If this is the case, it's the sensor and nothing you do with the grounds will fully resolve the issue. The thermocouple must be floating!

Just thought of another test but only for confirmation, connect a sturdy ground wire between the sensor sheath or engine location in which the sensor is attached to the 12V ground of the converter. This should more or less equalise the ground potentials and should reduce the false Pyro readings.

One final check of the problem as is: Measure the ground shift between the sheath and the 12V ground on the converter using a multimeter. I bet it changes and is non-zero under the operating conditions mentioned earlier. I have measured upto 2.5V ground shift between engines and chassis at different points in my past working life. Most sensitive automotive sensors today (thermocouples are a good example, as well as O2 sensors) need to be floating w.r.t. chassis ground because of the harsh electrical underhood environment.

Please post outcome of tests, discussions with Auto Meters & resolution.

Thanks and good luck.

Converter output insufficient

P.S. I'm pretty sure your converter is just fine but possibly undersized for a bass thumping stereo if only 5A. @ 12V, that's only 60 Watts and assuming 100% conversion to stereo output (not even close to 100% in reality), the converter is unlikely to do justice to the vast majority of modern stereos.

If you can find a part number and make, try to look up the specs of the converter.

Otherwise buy a reconditioned one from Samlex (cheaper than new). Again no affiliation. I'm going to be buying a replacement for mine in case of likely future damage (e.g. vehicle submersion).

I ordered a 20 amp converter from samlex...they have a local distributor. I'll try to dismantle the t-couple this weekend, I really don't understand how it could be damaged, it's only been in the truck a few days...and I know how careful I was installing it. If I did damage it, a new one will only last a short time in the environment of an offroad vehicle.

The readings it gives seem consistant with other posts for running temps...

I will post what I find...

Mszekely, you may not have damaged the thermocouple (may have come damaged or shorted. It is entirely possible and I have seen the odd duff, brand new, thermocouple in my work experience and, believe me, for in the application we use them in, we are careful @ CAD 200 a pop and a couple of hours replacement labour) or I might be barking completely up the wrong tree. For different, work reasons, I spoke with a thermocouple vendor yesterday and learnt that the ceramic powder insulation may not always be continuous (although desired, leaving pockets of bare sensor wire in close proximity to the sheath) from a manufacturing perspective. It always makes sense to check the thermocouple before installation for shorts and functionality, easy to forget though.

Is there anyone else out there on 'Mud that can disconnect their sensor from the Pyro and measure the resistance of each sensor wire to the sheath? I assume that there should be no short.

A call into Auto Meters tech support might be warranted, explaining the diagnosis to date.

(The reason the ground shift causes problems lies in the input circuitry of the Pyro. If it is a full differential input, the short to ground (common mode voltage) may not matter. Most "cheap" input circuits use a single ended, ground referenced amplifier and given the very low sensor signal, a shift in the signal due to the different ground voltage will probably cause a false reading. I don't know what circuitry Auto Meters uses, so the aforementioned is pure speculation on my part.)

Another thought, I don't suppose the thermocouple wire is tie wrapped or routed closely coupled to any major current carrying wires in your truck? Inductive coupling from the power wire to the sensor wire (microvolts per oC) could also be an issue. If yes, try routing differently and see if this resolves the problem.

Looking forward to the resolution.

I will be calling auto meter today, the induction theory may prove intersting, the signal wire from the t-couple does meet other wires as it goes through the firewall penetration by the heater motor...I'm going to re-route it through it's own penetration, and keep it away from everything I can...

I received some questions about the small and simple regulator I've build to feed the memory of my radio/cd-player (and anti-theft alarm/remote door opener)
I've created a schematic drawing which is added here.
It's nothing fancy and a real electronics guy might have some comments to it, but it's simple and it works (for over 8 years now)

If you look at the drawing, most important thing is little box right in the middle marked 'IC7812'. In fact this IC has to be named "LM7812'. At the bottom there is a little drawing of the actual piece of hardware.
It's a small 'plastic' thinghy with a metal backplate, called a TO-220 housing.
From the plastic housing three 'legs' are protruding (I marked them 1,2 and 3)

If you take this scheme to an electronics shop where they have some knowledge of electronics (and not just sellers of components) they will understand and being able to provide you with the necessary parts and can give some hints as how to build it.

I've put it (the regulator, the two capacitors and the diode 1N4001) in a small aluminum box (5 x 5 x 2 cm) this box also serves as a cooling element for the regulator, just by fixing the 7812 to one of the walls.

A word about the +12V connection between the converter and radio/cd-player.
My unit has no separate connection for providing power to the unit as a whole and the memory, which most do have.
If your's has separated inputs then just separate the memory lead from the existing converter and connect it to the diode 1N4001 and you should be fine.
(in this case omit the diode marked BY 500/1)
In my case I found that my home-build regulator was feeding the convertor as well as soon as the ignition was turned off, because my radio/cdplayer had no separate feeds for power and memory.
Therefore I added the diode marked BY 500/1
This is just a 5 Amp diode, any diode with a sufficiant rating (5-10 Amps) will do.
If your setup is similar to mine you can give it a try without that diode, and see what happens. Eventually add the diode.
Total costs? Dunno. My most expensive part was the little alu box. My total expense was something like 9-10 USD.

If you want to give it a try, recently small 'switching' regulators were developed.
They look exactly like the IC 7812 but are (if I'm right) named R7812 and are not widely available yet.
Where the LM 7812 has an efficiency of about 45% the R 7812 has one of about 90%. This means it will only draw half the amount. It is more expensive tho. The LM will cost about 2 US the R (I've been told) about 12-15.

Hope this will help. And don't forget to put a fuse in the line in between battery and your home-build converter, as close to the battery as possible!

Did the new converter solved your problem? i am having a simiar issue

https://forum.ih8mud.com/showthread.php?t=153644