Thanks Andrew for the ultra-fast and accurate reply.<br>The Zetex ZHB6718 is:<br>- cheap $1.30, single SO8 package for a complete 4 transistor NPN/PNP h-bridge<br>- low voltage: it loses < .1V at 1Amp current<br>- good on current: gain is >200 at <1Amp current, meaning drive current is <5mA.<br>
A slight issue: on page 7, safe operating area, full copper, dc, they
imply that it's only capable of 5v, 400mV- maybe I'll have to double up
to reduce current on each one? Had any experience with it? Seems
straightforward to integrate- the Propeller outputs 3.3V up to 50mA, so
you could connect it directly, right? <br>
Hanno<br><br><div class="gmail_quote">On Fri, Mar 14, 2008 at 4:29 PM, Andrew Errington <<a href="mailto:a.errington@lancaster.ac.uk">a.errington@lancaster.ac.uk</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div></div><div class="Wj3C7c">On Fri, March 14, 2008 12:22, Hanno Sander wrote:<br>
> Hi,<br>
> I'm looking for a:<br>
> - cheap (ideally <$5 with less than 5 parts)<br>
> - low voltage (battery powered, so 6-8Volt)<br>
> - high current (nominal ~500mA, but spikes to 1 or 2 Amps)<br>
> H-bridge to drive a geared "rc car" motor.<br>
><br>
><br>
> This must be a common problem for hobbyists, but I can't find a discrete<br>
> component that fits the bill. I've tried L293 and L298 which are cheap,<br>
> ok on current, but terrible for low voltage- since they eat 2 Volts- which<br>
> also heats them up over time.<br>
><br>
> I'm reasonably happy with the LMD18200T, but at $14, it's not cheap, and<br>
> with a minimum voltage of 12 volts, it doesn't do low voltage.<br>
><br>
> Mass-manufactured items, like toy robots, seem to make their own<br>
> h-bridges using FET's - is that the solution? Hanno<br>
<br>
</div></div>Take a look at the Zetex ZHB6718:<br>
<br>
<a href="http://www.zetex.com/3.0/product_portfolio.asp?pno=ZHB6718&h=52" target="_blank">http://www.zetex.com/3.0/product_portfolio.asp?pno=ZHB6718&h=52</a><br>
<br>
There may be a better/later version, and of course you need to add logic<br>
to drive the transistors (and not to let the magic smoke out), but I think<br>
it's a neat chip.<br>
<br>
HTH,<br>
<br>
A<br>
<br>
<br>
_______________________________________________<br>
Chchrobotics mailing list<br>
<a href="mailto:Chchrobotics@lists.linuxnut.co.nz">Chchrobotics@lists.linuxnut.co.nz</a><br>
<a href="http://lists.ourshack.com/mailman/listinfo/chchrobotics" target="_blank">http://lists.ourshack.com/mailman/listinfo/chchrobotics</a><br>
</blockquote></div><br>