Yes for the 3.3V Prop.
Supply is 9 Volt (battery), the 2N3906 feeds the 5V regulator (and 3.3 Volt regulator).
Diode is 1N4148.
John
Edit: attached is a better schematic of that section; P24, P25, and P26 go to prop I/O pins. Resistors show up as boxes with PCB Artist.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad. Mars Attacks! (1996)
Post Edited (johnfl68) : 11/7/2008 12:31:14 AM GMT
There are a couple of things I noticed.... the 10k resistor off of the supply should be lower to overcome the higher in-rush current of the Propeller.
That said, the second 10k resistor forms a voltage divider working against your current drive also.· I have attached a modification that should fix the problem without changing the functional design.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
That is a much more elegant solution, and works fine, with about 2.45 Volts for I/O #2 on button press (I didn't have a 15K res handy, so used a 10K + 4.7K for now, but will use 15K for the final production prototype).
I just don't do this enough any more, that the solution was escaping me, especially with the 2 resistor in series upon button press the old way.
Now, to make the changes on the board layout, make one more final check, and order a few demo boards.
Thanks again!
John
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad. Mars Attacks! (1996)
The 22k/15k voltage divider would allow the supply voltage to fall near 5V and still produce a valid I/O voltage.
The Diode could be optional... I used it to create a diode drop so that the diode within the I/O itself wouldn't trigger.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
The diode in the older circuit was keeping the high output from I/O 1 from triggering the input on I/O 2. With the voltage divider you have, there is only 0.26 volts on I/O 2 so this is to low to trigger, which is fine.
Hmmm - should I add a diode for reverse voltage protection on the +9v input from the battery? The case these are going into has the friction contacts for the 9 volt battery, so yes it is possible to hook it up backwards. I know the voltage regulators have reverse protection, but the transistor before them would would not.
John
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad. Mars Attacks! (1996)
The transistor is in a sense a "gated" diode, so it's fine.... the diode as I have it in the circuit will act just fine for reverse protection. You are right on the 0.26 volts on the I/O. Actually I simulated it at 240mV. ... but with the switch closed, and 9V at the supply, I thought 3.6V on the I/O might be a little high if it was present 'before' the Propeller actually received power. With the diode added, the diode drop of 0.6V lowers the voltage to about 3.4V after going through the divider.
Alternatively I could have used different resistor values, but I wanted to keep things simple and easy to find with standard resistor values.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/8/2008 1:36:24 AM GMT
Comments
Yes for the 3.3V Prop.
Supply is 9 Volt (battery), the 2N3906 feeds the 5V regulator (and 3.3 Volt regulator).
Diode is 1N4148.
John
Edit: attached is a better schematic of that section; P24, P25, and P26 go to prop I/O pins. Resistors show up as boxes with PCB Artist.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad.
Mars Attacks! (1996)
Post Edited (johnfl68) : 11/7/2008 12:31:14 AM GMT
There are a couple of things I noticed.... the 10k resistor off of the supply should be lower to overcome the higher in-rush current of the Propeller.
That said, the second 10k resistor forms a voltage divider working against your current drive also.· I have attached a modification that should fix the problem without changing the functional design.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Thank you, thank you, thank you!
That is a much more elegant solution, and works fine, with about 2.45 Volts for I/O #2 on button press (I didn't have a 15K res handy, so used a 10K + 4.7K for now, but will use 15K for the final production prototype).
I just don't do this enough any more, that the solution was escaping me, especially with the 2 resistor in series upon button press the old way.
Now, to make the changes on the board layout, make one more final check, and order a few demo boards.
Thanks again!
John
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad.
Mars Attacks! (1996)
The 22k/15k voltage divider would allow the supply voltage to fall near 5V and still produce a valid I/O voltage.
The Diode could be optional... I used it to create a diode drop so that the diode within the I/O itself wouldn't trigger.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Hmmm - should I add a diode for reverse voltage protection on the +9v input from the battery? The case these are going into has the friction contacts for the 9 volt battery, so yes it is possible to hook it up backwards. I know the voltage regulators have reverse protection, but the transistor before them would would not.
John
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
President Dale: I want the people to know that they still have 2 out of 3 branches of the government working for them, and that ain't bad.
Mars Attacks! (1996)
The transistor is in a sense a "gated" diode, so it's fine.... the diode as I have it in the circuit will act just fine for reverse protection. You are right on the 0.26 volts on the I/O. Actually I simulated it at 240mV. ... but with the switch closed, and 9V at the supply, I thought 3.6V on the I/O might be a little high if it was present 'before' the Propeller actually received power. With the diode added, the diode drop of 0.6V lowers the voltage to about 3.4V after going through the divider.
Alternatively I could have used different resistor values, but I wanted to keep things simple and easy to find with standard resistor values.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/8/2008 1:36:24 AM GMT