William At MyBlueRoom
New Member
I've attached a diagram from Nigels' terrific PIC site
It's a high side driver similar to the one on the Circuit Cellar site
**broken link removed**
Assuming T1 is a 2N3904 and T2 is a 2N3906
My question(s) is / are:
1) With a voltage of 24VDC what values & wattage would be ideal for the resistors to switch T2 for full current (200ma)
2) If I required more current say 400ma on T2 are there better choices for T2?
3) There is a HEXFET IRFL9014 version at the bottom of the Circuit Cellar article; would this be a better choice for higher current designs.
PS I'd love to use a UDN2985 and (hopefully) gang two outputs to get the 250ma max output of the device. Problem with the UDN2985 is finding them in Toronto, (the ULN2803 is easy to find)
In case you're wondering it's to drive four very large LED seven segment displays, the voltage is under 24v and the current can be as high a 60ma per segment (24ma works fine though) For the low side driver I was going to use a sn74246 but decided to use a larger PIC and a ULN2803 (more flexable too)
I'll post the schematics on my site when they're ready.
It's a high side driver similar to the one on the Circuit Cellar site
**broken link removed**
Assuming T1 is a 2N3904 and T2 is a 2N3906
My question(s) is / are:
1) With a voltage of 24VDC what values & wattage would be ideal for the resistors to switch T2 for full current (200ma)
2) If I required more current say 400ma on T2 are there better choices for T2?
3) There is a HEXFET IRFL9014 version at the bottom of the Circuit Cellar article; would this be a better choice for higher current designs.
PS I'd love to use a UDN2985 and (hopefully) gang two outputs to get the 250ma max output of the device. Problem with the UDN2985 is finding them in Toronto, (the ULN2803 is easy to find)
In case you're wondering it's to drive four very large LED seven segment displays, the voltage is under 24v and the current can be as high a 60ma per segment (24ma works fine though) For the low side driver I was going to use a sn74246 but decided to use a larger PIC and a ULN2803 (more flexable too)
I'll post the schematics on my site when they're ready.
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