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drill specs
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Glen
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drill specs

just trying to get some firm specs on drill drives so if anyone has specs such as current free load with a gearbox and red wheel on that would be super great, and also the actual rpm if anyone has the tools.

and if anyone has some firm data from within the bot like a telemetry thing that would be really nice. do they sell multi meters that can save info over a period of time?

Post Wed Jul 07, 2004 9:38 pm 
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andrew



Joined: 16 Jun 2004
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Location: Castle Hill, Sydney. N.S.W


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Hey all, i just did a test with the drill trigger (unmodified) and i tried it at 24 volts. There was a large spark, loug crack/bang and the actual FET on the heatsink exploded, theres only half of it still there then other half is gone somewhere else.

Just giving u the results though and telling all thinking of fiddling with drill triggers for speed controll that from what i have seen (and hoping to goodness that it works in my bot at 12 volts it works fine, havent tried 18 volt but since i dont have 18 volt nicad packs or something it doesnt matter but they CANT handle 24 volts.

That makes me glad that i am running my next machines drive at 12 volts then
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Post Wed Jul 14, 2004 1:04 pm 
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Spockie-Tech
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Those Fets sure like to go bang dont they ? Very Happy

I've never seen electronic components explode as enthusiastically as MosFets do when they decide they dont like what you are doing.. Still I suppose they are handling between 2,000 - 10,000 times (yes, seriously !) as much current as your average electronic device does, so its not surprising.

I read in a FET datasheet somewhere one of the best pieces of technobabble I've ever seen.. something about "Observe that the destruct lines behave linearly and extrapolate to zero device capability at a very high temperature consistent with mesoplasma formation" . That Mesoplasma must be explosive stuff. Laughing

MosFet = Magic Odor Smoke and Flame Emitting Transistor.

Post Wed Jul 14, 2004 1:19 pm 
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ffej
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quote:
do they sell multi meters that can save info over a period of time?


You can get multimeters that do save the peak current/lowest voltage, havnt got one myself, might look into getting one though. You'de be looking for a datalogger of some sort.
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Post Wed Jul 14, 2004 1:21 pm 
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Nick
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Meters that have a PC link often come with a basic datalogging software. I saw the results in a battery charger review - basically a plot of charge voltage over time that looked very good. Some of the meters at Jaycar do this and are not too expensive; $70 to start with. It would be ideal to log voltage AND current at the same time, but you would need a far more expensive solution to do that (or just use 2 meters?).
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Post Wed Jul 14, 2004 1:57 pm 
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kkeerroo
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A thing to remember about multi-meters is that you will proberbly not find one that will measure more than 10A. To measure more than 10A you will need a device called a "current clamp". The look similar to a multi meter but have a large clamp at one end which is placed around the wire that has the current to be measured passing through it. This means that they are much safer and easier to use as no physical conection is made to the circuit (The device measures the magnetic field generated by the current). But they tend to be expensive, $200 upward if memory serves me well.
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Post Wed Jul 14, 2004 4:41 pm 
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Nick
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Jaycar have a small clamp meter for $150. It's re-badged and sold by many places - Jacar is the cheapest i've seen so far. I have never seen a clamp meter that also does data logging. Perhaps there is an add-on for a normal meter out there somewhere...
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Post Wed Jul 14, 2004 5:03 pm 
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DumHed
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don't clamp meters only work on AC current, since they're an inductive pickup?
With no change in magnetic field (ie, not AC current) there'll be no signal generated in the clamp.

It should work for peak inrush currents on DC stuff, but accuracy will be questionable.

What you really need is a current shunt, which is a large, low value, high wattage resistor. Jaycar now sell current shunts, which is handy!
You can read the current by measuring the voltage across the shunt and I=V/R

Also, there's a clamp meter that works with a normal multi meter, and it's cheap. I think I paid $25 for mine.
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Post Wed Jul 14, 2004 5:08 pm 
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mytqik



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My father in-law is an electrician & he has am AC/DC current clamp meter with datad logging. Dont know how the clamp works, but it is very good. the meter it self has a small memory to record the data, & replay it, but also has a link to a PC for real time capture. It cant measure more than one thing at once.

The downside: $750 each Sad

Post Wed Jul 14, 2004 5:55 pm 
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Nick
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I think the DC clamp meters use a hall effect sensor - you have to 'zero out' the ambient field to get an accurate reading and after that it seems quite accurate, plus mine goes up to 200 amps.
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Post Wed Jul 14, 2004 6:28 pm 
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Totaly_Recycled
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Mine goes up to 1000 amps d/c Smile but it is a shunt type meter so it has a huge brass buzz bar (shunt ) that needs to be in series with the motor on test ..

Post Wed Jul 14, 2004 7:16 pm 
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Spockie-Tech
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I have one of the 50 amps jaycar current shunts (available up to 200amps i Think) and a datalogging meter (The$70 one), and they work quite well together. you get 1mv per amp, so the display just reads the amps if you ignore the decimal point. you do need to put it in series like andrew said though, rather than just clipping it around existing leads like a clamp meter

The logging software for the cheaper meter actually has some features that the more expensive meters dont have until you get into the really expensive ones - The ability to alter the sampling interval (IIRC). you can set it from 3 times per second to once per hour or more. they just use a Com port, so you probably could hook up two of them without a problem if you wanted to measure amps and current at the same time.

The alternative would be to make up your own little datalogger widget using a Pic-Axe micro. the 18 pin X version has a 10-bit convertor (1024 step resolution) with 3 analog inputs, and the ability to output RS-232 data to your PC's com port, so you could probably even imitate some other meters protocol and use their existing logging software if you didnt want to write your own.

Post Wed Jul 14, 2004 9:58 pm 
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Giant Robo
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@ Andrew Welch. Did you have the battery connected at the right polarity?
Andrew (Totally Recycled) showed me under the outer case, those drill controlers are rated up to 24V! ( It`s printed on them!) But said if you wire them up the wrong way round they deffinitely go bang! The last couple of days I have been shrinking down the version he taught me; with forward, reverse, steering with a mixer and braking. I havn`t test them on the 21.6V. that I want to run at but please tell me you might have just done a " Welchy" and wired it backwards Wink

Post Thu Jul 15, 2004 2:50 am 
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andrew



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I may have. Not too sure> ai am pretty sure i checked everything but i dont think i did. I very well may have but i am not 100% certain sorry mate. 21 volt should be right if all readings r correct and all. I just dont think they liked 24 volts. I have another one so i wil test the idea again but this time ill check everything
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Post Thu Jul 15, 2004 7:44 am 
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andrew



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Location: Castle Hill, Sydney. N.S.W


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I stand corrected there sorry. I did a welchy again and didnt check the polarity and all. I just ran one of my 18 volt drills at 24 volts and it seemed alright. Will do more extensive research and put some load to it (like when pushing another robot) and such and see if it can all handle the current and that nothing goes pop. Also need to get the reversing switch wired up and test it out sometime.

Also Glen, how the hell do u get this chuck off the 18 volt drill u have me. Its a absolute mongrel.
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Post Thu Jul 15, 2004 8:16 am 
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