Post by thread:pic max voltage

Does anyone know the max voltage you can run a 16c84 at ? I tried the other day, at about 8 volts it became unstable could this have been because it was misreading the eeprom ? I should try programming it at a higher voltage. But before I do, has anyone else done this ? It would be great if its possible to run direct from a 9 volt battery I am not bothered if the odd one gets fried in this application also as current drain will be very low I can use a large current limiting resistor of 330 Ohms or so in the supply line As a last resort suppose I could put a led in the supply line -- Peter Cousens email: spam_OUTpeterTakeThisOuTcousens.her.forthnet.gr phone: + 3081 324450, 380534 snailmail: Folia, Agia Fotini, Karteros, Heraklion Crete, Greece.

just put in a 78L05 or do you want jelly on your toast? michael -----Original Message----- From: Peter Cousens <.....peterKILLspam@spam@COUSENS.HER.FORTHNET.GR> To: PICLISTKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Date: Monday, March 30, 1998 12:00 PM Subject: pic max voltage {Quote hidden}>Does anyone know the max voltage you can run a 16c84 at ? > >I tried the other day, at about 8 volts it became unstable >could this have been because it was misreading the eeprom ? >I should try programming it at a higher voltage. >But before I do, has anyone else done this ? > >It would be great if its possible to run direct from a 9 volt >battery > >I am not bothered if the odd one gets fried in this application >also as current drain will be very low I can use a large current >limiting resistor of 330 Ohms or so in the supply line > >As a last resort suppose I could put a led in the supply line >-- >Peter Cousens >email: EraseMEpeterspam_OUTTakeThisOuTcousens.her.forthnet.gr phone: + 3081 324450, 380534 >snailmail: Folia, Agia Fotini, Karteros, Heraklion Crete, Greece. >

On Mon, 30 Mar 1998 08:54:27 +0300 Peter Cousens <peterspam_OUTcousens.her.forthnet.gr> writes: >Does anyone know the max voltage you can run a 16c84 at ? > >I tried the other day, at about 8 volts it became unstable >could this have been because it was misreading the eeprom ? >I should try programming it at a higher voltage. >But before I do, has anyone else done this ? The Absolute Maximum Rating is 7V. I suspect that the EEPROMS, both data and program, will be mis-biased at voltages higher than that and the chip will not function. Also, even if the PIC doesn't burn out right away, the high stress from excess voltage could cause it to fail very quickly. >It would be great if its possible to run direct from a 9 volt >battery It is better to drop the voltage down to about 3V, the PIC will use less current and battery life will be extended. A battery consisting of 3 or 4 AA or AAA cells in series could be connected to the PIC directly and run it for much longer than a 9V would. >>I am not bothered if the odd one gets fried in this application >also as current drain will be very low I can use a large current >limiting resistor of 330 Ohms or so in the supply line A simple regulator of a voltage divider with fairly large resistors setting the voltage to the base of an NPN transistor voltage follower could work. Of course there are reasonably-priced micropower 3-terminal linear regulators which would be ideal for longest battery life if that is important. >As a last resort suppose I could put a led in the supply line Yes, this is practical. Depending on the color of the LED about 1.5 to 3V will be dropped. And the power lost by the LED isn't completely wasted (as it would be with a linear regulator) since it could act as a pilot light. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]

Hi everyone!! >It is better to drop the voltage down to about 3V, the PIC will use less >current and battery life will be extended. A battery consisting of 3 or >4 AA or AAA cells in series could be connected to the PIC directly and >run it for much longer than a 9V would. > >>>I am not bothered if the odd one gets fried in this application >>also as current drain will be very low I can use a large current >>limiting resistor of 330 Ohms or so in the supply line > >A simple regulator of a voltage divider with fairly large resistors >setting the voltage to the base of an NPN transistor voltage follower >could work. Of course there are reasonably-priced micropower 3-terminal >linear regulators which would be ideal for longest battery life if that >is important. Anyway a 9V battery has a charge of about 100mAh. Any regulator you intend to use must have a very tiny bias current (78L05/LM317) so it would not "suck" the battery... I'd rather better use an IC or two NPN (2N3904/BC549C) with high hFE in Darlington configuration with resistors around 100k. That should do it. > >>As a last resort suppose I could put a led in the supply line > >Yes, this is practical. Depending on the color of the LED about 1.5 to >3V will be dropped. And the power lost by the LED isn't completely >wasted (as it would be with a linear regulator) since it could act as a >pilot light. > Other good idea is to use two CR2032 (3V-coin type) batteries! They have about 180mAh, are much smaller and much lighter then 9V batts and it's not too dificult to find holders for them! Check RS Components! http://rs-components.com Rafael Pinto

Hi Peter, I have noticed that the PIC starts drawing current above 7 volts, even with the clock stopped. At 8 volts output pins start moving away from supply rails and the chip doesn't work so well, like the complementary output transistor is starting to come on. Have lost pins at 9 volts, and the chip stops, but works again at normal voltages(without the pins that burned out). I won't trouble you with the typical off-topic replies, you already got many of those :-) Cheers, Bob

> From: Hardy e/ou Rafael Pinto <@spam@cppintoKILLspamNETRIO.COM.BR> > >It is better to drop the voltage down to about 3V, the PIC will use less > >current and battery life will be extended. A battery consisting of 3 or > >4 AA or AAA cells in series could be connected to the PIC directly and > >run it for much longer than a 9V would. > Anyway a 9V battery has a charge of about 100mAh. Yea. 9v * 0.1Ah = 0.9 Wh, but AA cells usually have 500-600mAh, 2AA : 3v * 0.5Ah=1.5Wh - more power! But if the device's price is not a problem - the best solution is to use DC/DC convertor, not linear regulator, and step-down convertor may be more effectivity then step-up. Alex Torres, Kharkov, Ukraine (exUSSR) KILLspamaltorKILLspamchat.ru 2:461/28@FidoNet www.geocities.com/SiliconValley/Lab/6311