can MegaStim handle 12V input?

[lamrith]

HEy all, may seem like a wierd question, but I am getting used to the MS here on the desktop. Seems like the 9V battery died pretty quickly. I have a pair of 12V7MaH batteries and was wonderinf if the stim could handle 12v input?? That way I can connect the bigger 12V batteries and do more testing and programming????

Let ke know. I have 2 MS to get testing and learning with and it will be a while before I can get them on car. I can recharge the 12V batteries easy, so save $$ versus buying 9V all the time....

[lamrith]

THANKS!!! Tht is gonna be a BIG help.. the 9V I had seemed to die pretty quickly... like maybe an hour combined run time over a few days with both MS..

[lamrith]

AWESOME!!! I have probably 5 of those laying around, now to find specs and see which one will be best.

[510rob]

I have an old "MS-salvaged" 13.5V Hitachi video camera supply powering my stim for running my V2.2 through a crude "burn-in" period. My stim's R9 is the 390ohm 1/2 watt resistor, and that poor little bugger is completely charred, but working fine. I will replace it with something a tad higher (680 or so) when I get over to the local elex shop soon, but I have left the setup running for several days to get it to that point. It's still working fine, but just looks wrong because the paint on R9 looks completely cooked.

My multiday burn in period revealed the stim's R9 to be a bit unnderrated when operated at 13.5 volts for extended periods. All other parts elsewhere seem ok. I'm planning to get a large high current supply and run the rest of the system including ignition for a few days to see what else, if anything, reveals itself to be unnderrated.

[510rob]

Lance,

When I took out R9 and measured it, I read 100 ohms, but just assumed some crazy degredation had taken place - I assumed it was a 390ohm resistor, but I was wrong. For future record, I bought this stim kit from Glen Hoag. It worked fine and as you said, could be left running all year long. I ended up taking out the charred looking 100 ohm resistor and replaced it with two 200 ohm 1/2 watts in series, both standing on end with a jumper connecting the two at the top end - that way, I can simulate vehicle conditions prior to starting the motor (powered up without an RPM signal)

I ended up getting a hefty bench supply that's good for 50amps, so I should be able to burn in the whold setup without any current-related problems MY concern is more about ignition noise and issues relted to spec'ing fuses and wire diameters for a few installations...

Robert F.

[Glen Hoag]

Robert,
When I started building stim kits, R9 was specified on the BOM as 100 ohms, as Lance mentioned. There was some discussion here in the forums a while back about changing it to 390 ohms so it wouldn't get so hot when running for long periods, especially off a power adapter. There may have been a month or so from the time the BOM was changed until I caught up with it; we didn't have a procedure in place at the time for Lance to alert distributors to BOM changes.

Your solution sounds reasonable, but I'd be happy to mail a 390 ohm resistor to you (or anyone else who bought a stim kit from me that included a 100 ohm resistor for R9). Just drop me a note.

--Glen

[510rob]

Glen,

Thanks for the helpful offer (and great post-purchase support I might add!), but the bag of five 1/2 watt 200 ohm resistors only cost me about $1Cdn and took all of 2 seconds to swap into place. I suppose on a group project of this nature, the 100 ohm vs. 390 ohm kind of change is bound to happen and people can't expect you to offer eternal support for global changes made after you've shipped things to them, but still, a very generous offer for support by yourself. My only reason for posting the info about sourcing the kit from you was for potential serachers looking for information about " R9 STIM 390 OHM 100 OHM "

Robert F.

[wsteele]

So I went through my rather large pile of Wall Warts and came up with only one that was close. It was 9v at 200 mA.

Will that cut it, or do I keep searching on Ebay for a cheap Wall Wart with something more like 12V @ 300+mA? I need another Wall Wart like I need a hole in the head.

I really am tired of buying 9V batteries at 3 bucks a pop.

[Fastest95PGT]

I'm not sure if 200mA will cut it..

Here's a quote from the Stimulator assembly guide..

AC/DC adapter from discarded household electronics if it has a 9 to 12 DC Volts at 300 to 750 milliAmps DC output

[wsteele]

Lance, that is what I figured as well. I am still in the assembly stages so I am not hooking it up for extended periods. I will just include keeping an eye on the power supply temp as a part of the testing.

Thanks again for all the help, things are really coming along.

[TimMoman]

A word of caution about wall-warts. Be sure your unloaded voltage is an acceptable level. Unloaded these guys can creep up and cause a voltage hit when you connect to your MS.

[wsteele]

TimMoman and Lance,

Thanks for the heads up on the unloaded voltage, you were right on, my "9V 200 mA" Wall Wart puts out an unloaded 14.5V, checking Lance's posts above I think that should still work.

I will give it a try, if I Zap something, I will start over. Thanks again for all your help, it is much appreciated.

[People16vT]

hey guys

i think we use a desktop computer 12v power supply

[deviousKA]

I second the PC power supply. I have been using them forever with mega and other projects, work great, and cheap.

Get an older AT style, with the mechanical power switch, you could get one used for under 5 bucks at any pc recycler.

[Bobzooki]

I just bought a 12V 1A wall wart at Radio Shack. It appears to be putting out more like 13.8 volts, but seems to work just fine.

[JET]

Does it matter if the adaptor is rated higher then recommended(300-700 mA)? I have a multi-voltage one(1000mA rated) that with a DMM puts out 12 volts unloaded(switch set at 12volts) and has a polarity switch that I can set to use the built in 9volt battery connector(without cuting the adaptor plugs off).I'd rather use that then a 9 volt/400mA one I have that puts out 14volts unloaded.My R9 is 100ohms.cheers

[elturbonitroso]

I have one that put DC9V 400mA can I used that one.

[jsmcortina]

A 9v supply should be ok, but I would aim for a 12v if available as it is closer to the normal working voltage.
My PSU puts out just under 15v at full voltage and has been driving my Megasquirts just fine for the last two years or so.

James

[cilegray]

You can also make your power supply adapter from a computer 4-pin molex connector (the white flat plugs inside a PC that connects everything to the power supply).

Use the yellow wire for + (+12V)
and any of the black wires for ground. On my ms I read 11.95-12.05v consistently.

[coyoteboy]

I have to add to the warning that was mentioned earlier about open-circuit voltage - two of the 12v wall-warts I tested last night were throwing out nearly 20v with no load Looks like ive got a use for that old AT power supply after all...