luminastrum
New Member
The "Getting Started" datasheet iilustrates that pin #1 on the 28X1 should be tied to +5V with a "4k7" ohm resistor. Does that mean 4.7K or 47K? Thanks.
Which Resistor for Reset Pin on 28X1?
- Thread starter luminastrum
- Start date
leftyretro
New Member
4,700 = 4k7 = 4.7K Ohms
demonicpicaxeguy
Senior Member
the colors are yellow-violet-red
however i have seen diagrams where it is just directly connected to +5v
however i have seen diagrams where it is just directly connected to +5v
As far as I can see the resistor alone doesn't do much (you may as well just tie the reset pin directly to 5V), unless you add a capacitor between the reset pin and ground (NOT between the resistor and the reset pin) - this then acts as a low-pass filter / power decoupling and prevents short glitches on the power supply from resetting the Picaxe.
The values are not critical, something like 10 kOhm and 10nF works well.
Wolfgang
The values are not critical, something like 10 kOhm and 10nF works well.
Wolfgang
Microchip:
"The behavior of the ESD protection on the MCLR pin
differs from previous devices of this family. Voltages
applied to the pin that exceed its specification can
result in both Resets and current consumption outside
of device specification during the Reset event. For this
reason, Microchip recommends that the MCLR pin no
longer be tied directly to VDD. The use of an RCR
network, as shown in Figure 14-5, is suggested."
- and if you want to see the figure you'll have to check the Data Sheet, whatever that is?
"The behavior of the ESD protection on the MCLR pin
differs from previous devices of this family. Voltages
applied to the pin that exceed its specification can
result in both Resets and current consumption outside
of device specification during the Reset event. For this
reason, Microchip recommends that the MCLR pin no
longer be tied directly to VDD. The use of an RCR
network, as shown in Figure 14-5, is suggested."
- and if you want to see the figure you'll have to check the Data Sheet, whatever that is?
For the 28X1 (PIC16F886) Data sheet, FIGURE 14-2: RECOMMENDED MCLR, the Circuit consists of a Resistor of 1kohm or greater between MCLR and VDD.
A Capacitor of 0.1uF between MCLR and ground is designated as "optional, not critical".
So I guess this means the Rev-Ed recommended 4k7R from Reset to VDD is OK. (So why did we not just accept their recommendation in the first place?)
A Capacitor of 0.1uF between MCLR and ground is designated as "optional, not critical".
So I guess this means the Rev-Ed recommended 4k7R from Reset to VDD is OK. (So why did we not just accept their recommendation in the first place?)
No-one has yet asked how big a switch and how heavy the traces, so I will....
It dosn't matter how big or small things are it's still called a short circuit.
In case of any lingering confusion ... the "no resistor, a push button and thick tracking" configuration was a sarcastic offering.
One can either connect the Reset direct to +V and never connect a reset button or use a suitable resistor ( 4K7 is common ) and either add a reset button or not. The PICmicro datasheets advises against using a direct to +V connection and recommends a resistor ( Section 14.2.2 ).
One can either connect the Reset direct to +V and never connect a reset button or use a suitable resistor ( 4K7 is common ) and either add a reset button or not. The PICmicro datasheets advises against using a direct to +V connection and recommends a resistor ( Section 14.2.2 ).
...that last bit is nearly same as I quoted from Microchip earlier (check it out) , though actually it recommends RCR.
Habing said all that, I've never had any problems ever with using 4k7 to 10k between MCLR/Reset and +5V. End of.
I would never connect directly. Asking for trouble, esp for newbies.
This is another subject that strangley appears from time-to-time and really should be nailed.
Habing said all that, I've never had any problems ever with using 4k7 to 10k between MCLR/Reset and +5V. End of.
I would never connect directly. Asking for trouble, esp for newbies.
This is another subject that strangley appears from time-to-time and really should be nailed.
demonicpicaxeguy
Senior Member
i do on every pic i use use the 4.7k resistors
one of the things i've seen the mclr pin connected directly to 5+ was on a sound activated paintball hopper controller, which had failed
i think some of the confusion also gets started by a few of the "pic projects" out there ,where people have just done that and show the mclr pin conected to 5+ on the schematic
one of the things i've seen the mclr pin connected directly to 5+ was on a sound activated paintball hopper controller, which had failed
i think some of the confusion also gets started by a few of the "pic projects" out there ,where people have just done that and show the mclr pin conected to 5+ on the schematic