Re: [CAD_CAM_EDM_DRO] Chopper max voltage?

Hi-ho,

I don't want to disagree with Dan, as I'm sure he's done his homework, but I
suspect he has no heatsink on his modules? In which case they would
definitely expire if you used a higher rail voltage.

I'm running the 35V controller with a set current of 1.8A. I'm also using a
circuit which cuts the holding current back to .5A after about 2 seconds of
no step signal. I just used a 555 timer for a monostable (one-shot timer)
and drive a bilateral switch circuit that switches between two set pots.

The 298's are on a good sized heatsink, with a fan.. If the machine is
running a long job the heatsinks still get warm to the touch, but I've not
had it fail yet (touch wood).

Cheers, Chris.

* Design engineer, Assembly worker, Cleaner.
* Ohmark Electronics. PO Box 5302, Christchurch, New Zealand.
* http://www.ohmark.co.nz

----- Original Message -----
From: Mike <mnels@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Thursday, October 05, 2000 5:41 AM
Subject: Re: [CAD_CAM_EDM_DRO] Chopper max voltage?


> At 05:57 PM 10/4/2000 +1300, you wrote:
>
> >The rating of the L298 is 46V, and absolute max 50V.
> >
> >I've personally run them at up to 35V without any problems.
>
> Dan Mauch claims the L298 won't run over 18 volts, even with a big
> heatsink, without getting too hot if you're running anywhere close to 2
> amps with it. He sells a L298 based board so I assume he'd know?
>
> I know the datasheet specifies much higher voltages, but they also specify
> a maximum power dissipation value. I suspect it's a complex combination
of
> frequency, current, voltage and perhaps even the inductance of the motors
> that determines how hot the L298 will get.
>
> So is Dan just trying to sell his bigger 5 amp controller or does the L298
> really get too hot over 18 volts? How much current are you running at 35
> volts?
>
>
>
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