The trick is driving the high side transistors T1 & T3.  When they are
ON, their emitters are near VCC and the control voltage must be higher.
Try PNP for T1 & T3 and drive them through an inverter.

Sherpa Doug

> -----Original Message-----
> From: Edson Brusque [mailto:ebrusque@TERRA.COM.BR]
> Sent: Thursday, June 28, 2001 4:27 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: How to make a PIC control de rotation and direction
> of a 12VDC motor.
>
>
> Hello people,
>
>     first, sorry for the attached .GIF, it's only 10K, so I
> think nobody
> will complaim. :)
>
>     Second, thank you for the replies about the h-bridge.
>
>     The attached schematic is of an h-bridge I'm making on a
> proto-board
> right now. It's working very well. VCC is at 12 volt. When
> CONTROL-1 is high
> (at 12V), I have rotation clockwise. When CONTROL-2 is high
> (at 12V), I have
> rotation anti-clockwise (or is this conter-clockwise?).
>
>     Actually, this circuit doesn't work well with logic
> levels. But maybe I
> could use some pullup resistor and use a PIC output to drain
> current to
> ground the CONTROL-X inputs.
>
>     What are your thoughts about this circuit?
>
>     Best regards,
>
>     Brusque
>
> -----------------------------------
> Edson Brusque
> Research and Development
> C.I.Tronics Lighting Designers Ltda
> (47) 323-2138  /  (47) 9993-6453
> Blumenau  -  SC  -  Brazil
> www.citronics.com.br
> -----------------------------------
>
>

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