The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by 49 Custom, Feb 19, 2010.
I also used the same LM7806 without the capacitors and it works just fine for the fuel gage on my 37 Chevy.
I'd be worried about tantalums surviving a load dump transient.
The other caps mentioned would be preferrable IMHO.
Filter caps are not necessary in most pure DC applications. Additionally, the LM7806 has internal filters that provide 70+ dB of ripple rejection...every 6 dB of rejection cuts the voltage in half, so the internal filters will halve the tiny ripple voltage 12 times, rendering it irrellevant. It is true that the capacitors don't cost much, but they do provide another possible point of failure, and the classic capacitor failure mode is dialectic breakdown, which is essentially a short. In this circuit, that means a short to ground. I wouldn't use them in this application, but I am sure there are other engineers who would because redundancy seems to be a popular theme in the field.
great thread! these vr's are really great and are small. last one i did i used old heat sink off computer fan.
Please note the location of these eBay items before you order!
I just ordered 10 to see what I got. I had the same thoughts you expressed. I'll let everyone know how it turns out.
For $4 with free shipping, considering they are probably made over there anyways, I'm not too worried about it.
If I lose my $4, I'm not really going to worry about it. I'll just have to skip drinking a few beers on Friday night.
Ford used a resistor wire instead of an actual ballast resistor for coil circuits, sorry I don't have a part number. But I took one cut it in half and used it as the dropping resistor for a 6v ahooga horn on a 12v car. Maybe try a ballast resistor for the wipers.
Great tech article.
I've been using Mopar starter relays for years for these horns with no failures! (And lots of usage)
Great post on the regs, I love stuff like this!
A starter relay would definitely handle the current from a 6V horn on 12V. My comment was meant for the 12V horn relays used to replace the 6V horn relays in most applications - work fine with 12V horns, but not so well with 6V horns on 12V and double the current.
For those of you who don't want to or can't solder or want an OEM alternative solution here's a little pricier option. Pretty much every Ford vehicle up through at least well into the 1970s (probably into the 80's as well) used fuel/oil/water gauges that operated on 5-6 volts. They never changed them...probably not until quite recently.
SO, what that means is that every single Ford from the 1930's up to who knows when had 6V gauges and when 12V negative ground systems came into play they also had a voltage regulator on the the gauge panel and/or in-line to help keep the gauges alive and happy at 5-6 volts ....this is also sometimes refered to as a 'voltage stabilizer' if your talking to some parts guys. The cars, truck, vans, etc from around 1960 through 1969 had an easy to adapt regulator that looked like the one here. All you need is a place to screw it down and just plug it in. The Motorcraft part number is/was SW6325. IF the kid running the computer needs an application because he doesn't know what a book/cataloge is then just ask for one for a '68 F100 or a '68 Mustang. I think NAPA still carries them, some of the better/older parts stores may carry them as well. The Ford restoration places all carry them. Just be sure to get one for a 1960-1968 Ford anything. Some 69's and most everything after 1970 had a similar design that 'snapped' into a flex circuit on the gauge panel....less user friendly for us hotrodders.
It just gets better and better, thanks!
BigChief - aren't those just chopper circuits? Not that it would matter much with early Ford gauges...
Please school me, will one still be needed for each gauge? Thanks, Dave
Nope, one for the whole sha-bang!
Thanks for that info. I have an old 6v swoop tacho that goes to 6000rpm I want to run in my dodge, problem now solved.
FWIW, Motorcraft # SW6325 crosses to Ford # 6L2Z13D730BAA, Napa and Autozone can't cross this number, dealer only item?, retail price at local dealership, $103.56, ouch!, 4 runtz type...$60.00...Dave
NAPA still has these, around 9-12 bucks. Called an IVR. Used into the '90s on large box trucks, maybe others...
Also, those snap fittings are the same as 9v battery ones.
Hey 50chevy, you wouldn't have a NAPA number would ya?, IVR stand for instrument voltage regulator?...Dave
And $0.10 for an L7806 CVR...
Cool idea. I don't have gauges I need to reduce the voltage on, but I was wondering how much power/amps a power transistor in the circuit would handle? I have a 6V ah-oo-gah horn I want to use on my 12v system.
Oops! Just finished reading the rest of the posts, should have before I posted. I will not run by 6v Ah-0oo-gah horn on 12v however as it is not a regular horn and I do not want to burn it up. I will look into a ceramic resistor type.
I wanna see MORE of the bike in your avatar
Napa number is ECH IR1
I definitely looked into other solutions such as the IR1; what I liked about the separate LM7806's was that it made it easier to sort problems by segragating each circuit and much more cheaply. For those who are curious, the "old" Ford component mentioned above is electomechanical and works in a similar fashion to a points system. If you manage to find one on a junked 60's-70's Ford, it should be just fine. (I also own a '66 Mustang, so I can vouch for their durability!)
Someone else also asked about using a power transistor to increase the usable current on an LM7806; it definitely can be done and uses only one IC. Downside is that it requires a much larger heatsink and a safe place to mount it. (There were a couple of posts that mentioned that a heatsink wasn't necessary at all for the LM7806; naturally it depends upon the draw from your gauges. I suggested it to be on the safe side and meet everyone's needs.)
Thanks for all the comments, folks!
Thanks, how do you convert an ammeter to a voltmeter? Frank Kunkel
Do you have a RS part no. for the heatsink?
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