Grounding inputs.
- Thread starter eclectic
- Start date
Yes it would work. In fact in theory you don't actually need the resistor as the inputs are fixed as inputs, just tie them to 0V.
However care needs to be taken on chips such as the 08M where the pin could be an output, as this circuit would damage the chip if pin is converted to an output.
However care needs to be taken on chips such as the 08M where the pin could be an output, as this circuit would damage the chip if pin is converted to an output.
westaust55
Moderator
Grounding inputs
eclectic,
a thought . . . .
if I was going down the path of tying down unused or all inputs then I would go the way of your circuit 1 at the expense of a few more resistors.
Reason is that if you have a logic input from another IC you could still wire direct to the input pin without removing the resistor. Could even work with some items such as an LDR with the LDR between +5V and the input pin.
Would still need to remove the resistor if using a device that needed a pull-up resistor (such as a DS18B20 temp sensor)
One way depending upon your board might be to have the resistors soldered to plugs and inserted into sockets. I use this approach for the two pull-up resistors for the i2c bus on my AXE-022 proto-board. If another board already has the resistors (eg an AXE-033) then it is easy to remove these from the proto-board.
WestAust55
eclectic,
a thought . . . .
if I was going down the path of tying down unused or all inputs then I would go the way of your circuit 1 at the expense of a few more resistors.
Reason is that if you have a logic input from another IC you could still wire direct to the input pin without removing the resistor. Could even work with some items such as an LDR with the LDR between +5V and the input pin.
Would still need to remove the resistor if using a device that needed a pull-up resistor (such as a DS18B20 temp sensor)
One way depending upon your board might be to have the resistors soldered to plugs and inserted into sockets. I use this approach for the two pull-up resistors for the i2c bus on my AXE-022 proto-board. If another board already has the resistors (eg an AXE-033) then it is easy to remove these from the proto-board.
WestAust55
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Westaust55.
Perhaps I should have explained further.
It's for a bike rear-light.
At the moment, the Mark I, (18X) , is in a 25mm bore acrylic tube.
The final verson will be totally sealed and externally powered.
I'd like to try 19mm or even smaller.
The 20M (lengthways), is worth a try, using veroboard.
(I shudder at the thought of SMD!)
The first circuit is with 0.125W resistors
The second with just wires.
The third shows the wires soldered in under the Picaxe.
If I retain the LDR, it's a simple matter (beforehand) to use input 0 (leg 10)
e.
Perhaps I should have explained further.
It's for a bike rear-light.
At the moment, the Mark I, (18X) , is in a 25mm bore acrylic tube.
The final verson will be totally sealed and externally powered.
I'd like to try 19mm or even smaller.
The 20M (lengthways), is worth a try, using veroboard.
(I shudder at the thought of SMD!)
The first circuit is with 0.125W resistors
The second with just wires.
The third shows the wires soldered in under the Picaxe.
If I retain the LDR, it's a simple matter (beforehand) to use input 0 (leg 10)
e.
Attachments
hippy
Ex-Staff (retired)
I'd be tempted to leave them open-circuit or straight to 0V, but in this case, here's a clever trick ...
Don't cut the tracks underneath the 20M's ! That will link inputs to outputs without causing any major problems for the outputs and is a lot less work. Obviously cut the track where you need to bring an input from the other 20M
If you were going for maximum density and didn't care too much for maintainability, you could piggy-back one on top of the other rotated 180 degrees. The unused inputs of the top going to the outputs of the bottom ( which I'd keep for driving the LED's ) with the other legs cut off or bent out with flying leads. You could even cut off the unused input legs.
Don't cut the tracks underneath the 20M's ! That will link inputs to outputs without causing any major problems for the outputs and is a lot less work. Obviously cut the track where you need to bring an input from the other 20M
If you were going for maximum density and didn't care too much for maintainability, you could piggy-back one on top of the other rotated 180 degrees. The unused inputs of the top going to the outputs of the bottom ( which I'd keep for driving the LED's ) with the other legs cut off or bent out with flying leads. You could even cut off the unused input legs.
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hippy
Ex-Staff (retired)
I understand how you mean now. In that case, if you're using vero-board you can allow the output tracks to come out both sides of the 20M. Do it one one-way (N), next the other-way (S) in sequence and you can then put every LED across two adjacent tracks. With +5/0V split on the N/S side you can probably use a very clean half LED's to +5V, the rest to 0V. I'd probably solder direct to the vero-board, no socket.
westaust55
Moderator
Ah, so the old chestnut of insufficient information.
Input grounding resistors for the PICAXE are not essential for most purposes as Hippy has indicated and are used more as part of power/current limiting schemes where minimal power consumption is the priority. One exception, from my recent readings, seems to be where some analogue inputs will be used for analogue purposes and some for digital purposes.
Technical/Moderators,
Maybe an add-on to an existing or new Sticky post flagging the importance of people giving the maximum information on purpose, aims, schematics and code to reduce the time others spend trying to help before the problem can be solved.
Input grounding resistors for the PICAXE are not essential for most purposes as Hippy has indicated and are used more as part of power/current limiting schemes where minimal power consumption is the priority. One exception, from my recent readings, seems to be where some analogue inputs will be used for analogue purposes and some for digital purposes.
Technical/Moderators,
Maybe an add-on to an existing or new Sticky post flagging the importance of people giving the maximum information on purpose, aims, schematics and code to reduce the time others spend trying to help before the problem can be solved.