--- In , "dongle241" <patcooper@m...> wrote: > --- In , "vansykes" <vansykes@u...> wrote: > > Hello, > > > > I am building a sunroof control system for a friends car. It will > > automatically close the sunroof from the tilt or slide position > when > > Checkout http://www.allegromicro.com/sf/2001/ your device may be > listed, note the comments about series resistors. Also look at > http://www.allegromicro.com/datafile/2001.pdf just to get a feel for > the device design specs. Note the average input current is less than > 1mA. > > Personally I would ditch the driver and go for a modern octal device > such as the ULN2803. > > Did you measure the current (150mA) in series with the input pin ?. > > Cheers > > Pat Sorry, I checked the specs on the darlington sink driver I was using, it was well within spec. So then I analyzed how I measured the current. I did it between the power supply and the diode on the prototyping board. My mistake was that I had a jumper on the bottom side taking 12 volts to drive the relays. So I wasn't just measuring the current through the basicx, I was measuring all of the current. I measured a individual pin on the darlinton, and it is only taking 1 mA, so all is fine. Thank you for your suggestions, Vance Sykes

--- In , "vansykes" <vansykes@u...> wrote: > Hello, > > I am building a sunroof control system for a friends car. It will > automatically close the sunroof from the tilt or slide position when Checkout http://www.allegromicro.com/sf/2001/ your device may be listed, note the comments about series resistors. Also look at http://www.allegromicro.com/datafile/2001.pdf just to get a feel for the device design specs. Note the average input current is less than 1mA. Personally I would ditch the driver and go for a modern octal device such as the ULN2803. Did you measure the current (150mA) in series with the input pin ?. Cheers Pat

Try putting transistors inbetween the pins and sink driver. John Baker http://www.geocities.com/johnsrobotics/ vansykes <> wrote: Hello, I am building a sunroof control system for a friends car. It will automatically close the sunroof from the tilt or slide position when the car is turned off. The project has grown, since now I am now utilizing a 4 line Serial LCD+ to display the time, date, and control sunroof functions (4 buttons installed on a face plate with the LCD). I am using a 7 channel Darlington Sink Driver to drive 4 automotive relays to control the four motions of the sunroof(slide open, slide closed, tilt open, tilt closed). I am almost complete with the project, I was doing some final testing, I measured the current through the basicx chip, it is below 25 mA unless I activate one of the relays, then it goes up to 150 mA, which is 100 mA to much power draw according to the specs on the chip. I have to set a output high to turn on a relay through the Sink Driver. I need to figure out how to drop the current on the outputs controlling the relays. Any ideas would be greatly apreciated. Thank you, Vance Sykes --------------------------------- Yahoo! Groups Links To ---------------------------------

--- In , "vansykes" <vansykes@u...> wrote: > Hello, > > I need to figure out how to drop the current on the outputs > controlling the relays. Depending on how much current you need to control, there are several options. A simple, low current option is to use a driver like the 74LS06 which has high voltage outputs. It can sink 40ma and can withstand 30V on its output. If you need to sink more current, you can go with specialized driver chips like the ULN2803 which can sink 500ma and withstand 50 to 90V on the output. Or, you can use discrete driver transistors like the TIP120 which can sink up to 5A. Since you're driving relays, you'll need snubber diodes to protect the driver from back emf spikes when the relays are de-energized. The ULN2803 and TIP120 have them built in; other devices may need external diodes. With discrete transistors, you have a choice of outputting a high voltage to turn them on or a low voltage to turn them off. While this may sound like "same-same", it's actually not. In the former case, the BX output needs to source the current to activate the driver. In the latter case, an external resistor provides the current to activate the driver and the BX output simply clamps the driving voltage to ground and sinks the current that would otherwise activate the device. This distinction is important because the BX outputs can sink more current than they can source. Either way, depending on the device that you select and how much current it required to control the relays, you may need a two stage driver. For example, you might connect a BX-24 output to the input of a 74LS06 driver. The output of the driver would be connected to the base of the actual driver transistor (e.g. TIP120) which also has a resistor connected to a positive voltage (5V or 12V, for example). A low output on the BX would cause the '06 output to float high, switching on the transistor thus energizing the relay. This is backwards from your current logic but that's easy to fix.

> ... it is below 25 mA unless I activate one of the relays, then it goes up to 150 mA... You aren't powering the relays from pin 21, are you? You should get the power for any significant load, like relays, directly from the main supply, from a separate supply or from a separate regulator. Or are you overdriving the Darlingtons? They probably don't have internal base resistances so you cannot connect them directly to a BX-24 pin; put at least a 1K resistor between the BX-24 and the Darlington base, if you haven't done that. Tom Tom Becker --... ...-- www.RighTime.com The RighTime Clock Company, Inc., Cape Coral, Florida USA +1239 540 5700

Hello, I am building a sunroof control system for a friends car. It will automatically close the sunroof from the tilt or slide position when the car is turned off. The project has grown, since now I am now utilizing a 4 line Serial LCD+ to display the time, date, and control sunroof functions (4 buttons installed on a face plate with the LCD). I am using a 7 channel Darlington Sink Driver to drive 4 automotive relays to control the four motions of the sunroof(slide open, slide closed, tilt open, tilt closed). I am almost complete with the project, I was doing some final testing, I measured the current through the basicx chip, it is below 25 mA unless I activate one of the relays, then it goes up to 150 mA, which is 100 mA to much power draw according to the specs on the chip. I have to set a output high to turn on a relay through the Sink Driver. I need to figure out how to drop the current on the outputs controlling the relays. Any ideas would be greatly apreciated. Thank you, Vance Sykes