check out LT1083 too, it is a robust IC, low noise, low ripple, 7.5 ampsQuote:
Originally Posted by VDX
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check out LT1083 too, it is a robust IC, low noise, low ripple, 7.5 ampsQuote:
Originally Posted by VDX
... I'm using until 5 of the LM317 (fix set up to 1A each continuous) or LM338 (up to 2A) in a driver with 5 jumpers, switches or relays - so it's possible to set the max. current in coarse steps from 0.5A to 9A and fine-tune it by PWM of the source with a MOSFET to any value from 0 to max set without problems.
With a single LT1083 (I've tested this too) it's more complicated, as here I have to adjust the sense resistor for the max. current ... and with the single TO-220 housing it has a much smaller heat dissipation capability than 5 of the LM's ;-)
Viktor
excellent! thanks :)
that would be an interesting setup
... in post #3 I've linked to a wiki-page I've set up for some laser-cutter infos ... here the mentioned driver in detail: http://reprap.org/wiki/File:9Amp-driver.jpg
Using is as easy as shown in the schematics in the wiki, the sense-resistor defines the current per LM ( I[A] = 1,25[V] / Rs[Ohm] ), the 0R22 resistors (smaller for higher currents) 'harmonize' the single LM's, so the summed currents will be averaged without oszillating, and PWM-driving the diode is done by switching the power to the network through a MOSFET (single TO-220 on the left side)
Viktor
so what driver can i make?
i am not an expert in soldering, but my friend helps me with that
they put diodes in spec'd at 1watt and run them at half power? that seems a strange thing to do?Quote:
Originally Posted by VDX
... I think, it's a matter of heat-dissipating (sizes/prices of coolers) and enhanced lifetimes with 'underpowering' the laserdiodes ...
@mrfloppy - look at the specs of a LM317, decide, which current/power is enough and select the sense-resistor for this ... e.g. a driver for roughly 0.5Watts and 570mA is made with a single LM317 and a resistor with 2.2 Ohms (common used 2Watts or 5Watts-types) ... and an appropriate cooler for the LM ...
Viktor
They're not underpowered per se, but they're pulsed in the projector. Much less heat output. They need to be pulsed because a DLP projector produces different colours by rapidly changing between colours, then rapidly moving the mirror array, turning on the mirrors needed for that colour.