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In lugnet.robotics.handyboard, "Barrus, Brad" <bbarrus@cabletron.com> writes:
> I am trying to run a light with the motor outputs on the handy board. I
> looked up the spec on the L293D and it claims to be capable of 600mA
> constant and 1.2A peak. The miniature light I am using draws about 300mA.
> When the light comes on the handy board just dies (looks like too much
> current is being drawn). Any one have a similar experience? Know how to fix
> it?
> Thanks Brad
As others have said, the system should be able to drive this. However there
are some obvious 'thoughts':
1) A light that draws 300mA when running, will _momentarily_ draw a much
higher value when the bulb is cold. The actual ratio between the 'running',
and 'cold' currents, depends on the type of bulb, and the resistances of the
wires and batteries. It is possible that your bulb is just drawing a little
too much in this state. In projection bulbs (a lot larger), it is common
practice to have a thermistor wired in series with the bulb, to reduce the
'shock' on the filament as the bulb starts, and to keep this current below the
fuse rating. You could try the simple experiment of putting something like a
3.9ohm resistor in series with the bulb. This should keep the initial current
low enough, and when the bulb is running only 'lose' about 1v.
2) Though the drivers can handle this load, can your power supply?. If you
have a 'old' battery pack that is showing a high internal resistance, it may
simply be that the supply droops so badly when the load is drawn, that the HB
resets.
Good Luck
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Message is in Reply To:
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| I am trying to run a light with the motor outputs on the handy board. I looked up the spec on the L293D and it claims to be capable of 600mA constant and 1.2A peak. The miniature light I am using draws about 300mA. When the light comes on the handy (...) (25 years ago, 6-Apr-00, to lugnet.robotics.handyboard)
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