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Mark M Guest
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Operating at >100 deg C |
Posted: Mon Sep 27, 2004 7:17 pm |
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Hi,
Does anybody has any experience with running PIC 16F876 I/P at temperatures > 100 deg C and <130 deg C?
Data sheet implies it can be done but all parameters are spec'ed for temperatures between -40 and +85 deg C. I think RC osc is out of question as internal OSC will drift too much, so crystal ( hi temp ? ) or ceramic osc?
Mark M. |
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Guest
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Posted: Tue Sep 28, 2004 12:14 am |
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Crystal. But could you pull off your PIC board out from boiling water? |
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Mark M Guest
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Operating at >100 deg C |
Posted: Tue Sep 28, 2004 9:07 am |
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Not without gloves. But environmental chamber can cool it off for safe touching. I don't think pulling it out matters that much. Important for me is if PIC will still work at high temperatures.
Mark M. |
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arun Guest
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RE: |
Posted: Wed Sep 29, 2004 8:26 am |
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Hi,
No it does'nt work.
We tried to run a datalogger system which had a PIC 16F877 ; at around 60-70 degC , but it went haywire, it was unable to write to a external EEPROM, also had trouble communicating through RS 232.
Maybe you should design a thermal proofed unit so it is well protected from high temperatures, also you could go in for MIL grade instead of the standard commercial ones.
thanks
arun |
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Ttelmah Guest
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Re: Operating at >100 deg C |
Posted: Wed Sep 29, 2004 2:50 pm |
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Mark M wrote: | Hi,
Does anybody has any experience with running PIC 16F876 I/P at temperatures > 100 deg C and <130 deg C?
Data sheet implies it can be done but all parameters are spec'ed for temperatures between -40 and +85 deg C. I think RC osc is out of question as internal OSC will drift too much, so crystal ( hi temp ? ) or ceramic osc?
Mark M. |
A lot will depend on which temperature range devices you can get. The standard chips seem quite sensitive in various areas (I have seen the watchog in particular drop below the minimum specified time value, if you go above the maximum rating). However CCS, do sell versions that are warranted to 125C, and I have used these on a couple of units that required both operation and test over 100C, without problems. There are some significant 'caveats' (the internal EEPROM life drops to only 1/10th the normal value). You must also design the code to work right 'to' the limits, and not assume anything close to the 'typical' values will be occuring at these temperatures...
The data sheet for versions that are available in the higher temperature range, usually has an extra table showing this. Talk to MicroChip, and see if the chip you want to use is available in the extended temperature range version.
Best Wishes |
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Haplo
Joined: 06 Sep 2003 Posts: 659 Location: Sydney, Australia
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Re: Operating at >100 deg C |
Posted: Wed Sep 29, 2004 5:39 pm |
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Ttelmah wrote: | However CCS, do sell versions that are warranted to 125C. |
erm...Microchip. CCS compilers should work at any temperature as long as your PC can handle it ![Wink](images/smiles/icon_wink.gif) |
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Ttelmah Guest
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Re: Operating at >100 deg C |
Posted: Thu Sep 30, 2004 2:22 am |
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Haplo wrote: | Ttelmah wrote: | However CCS, do sell versions that are warranted to 125C. |
erm...Microchip. CCS compilers should work at any temperature as long as your PC can handle it ![Wink](images/smiles/icon_wink.gif) |
:-)
You mean CCS dn't do a high temperature compiler. That would explain a lot of the problems!...
Best Wishes |
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Mark M Guest
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pic oprating at temp > 100 deg C |
Posted: Thu Sep 30, 2004 10:06 am |
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I checked with Microchip and data sheet says that the E version is spec'd for up to 125 C operating temp. but it won't work off 3 - 4.5VDC and we are using a 3 x 1.5V battery. This going to be another problem. I have to ask Ttelmah, if he could hint me on batteries that will operate at temps > 100C.
Another "murky" thing is that in the MCP data sheet the LF876 part is spec'd as operational at bias up to 125 deg C but parameters at elevated temperatures are specified only for "E - extended" grade parts. The LF parts don't carry "E" suffix. Since our device has to run down to 3VDC and E part needs at least 4.0V, it looks like we have to redesign our device to have 6V battery with 4.5V or so regulator. I was thinking that just getting better parts will do withour redesigning.
Do you, guys know in MCP makes mil spec PIC's?
Mark M. |
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Ttelmah Guest
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Posted: Thu Sep 30, 2004 12:00 pm |
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Try 'Electrochem'. They did Lithium batteries in glass fibre cases rated to 200C!...
Best Wishes |
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Guest
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Re: pic oprating at temp > 100 deg C |
Posted: Thu Sep 30, 2004 5:32 pm |
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Mark M wrote: | I checked with Microchip and data sheet says that the E version is spec'd for up to 125 C operating temp. but it won't work off 3 - 4.5VDC and we are using a 3 x 1.5V battery. This going to be another problem. I have to ask Ttelmah, if he could hint me on batteries that will operate at temps > 100C.
Another "murky" thing is that in the MCP data sheet the LF876 part is spec'd as operational at bias up to 125 deg C but parameters at elevated temperatures are specified only for "E - extended" grade parts. The LF parts don't carry "E" suffix. Since our device has to run down to 3VDC and E part needs at least 4.0V, it looks like we have to redesign our device to have 6V battery with 4.5V or so regulator. I was thinking that just getting better parts will do withour redesigning.
Do you, guys know in MCP makes mil spec PIC's?
Mark M. |
Use a DC_DC converter 3V in and 5V out. Check Maxim they have several that will do the trick.
Another problem you will have the the choice of of the other passivc parts, capacitors being the main problem area.
PIC's are known to be "ok" at extreems.
You may also consider selecting the PIC parts by testing them yourself.
Many Lithium batteries are rated at 100oC and over .
100oC is high, down hole logger's deal with much higher temperatures. |
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Mark M Guest
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Posted: Fri Oct 01, 2004 9:25 am |
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Thank you all very much. You have been very helpful.
Mark M. |
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Will Reeve
Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England
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Posted: Fri Oct 01, 2004 9:31 am |
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I’m using a MAX682 in two current designs and they work very well. Both devices run off 3 x AA batteries. One Alkaline the other NiMH, so 4.5v and 3.6v in respectively. Only external components are three capacitors. I use 0805 size chip ceramic capacitors which will handle 125deg (amazingly you can get 10uF in this package size!). The IC only does +85deg so you might have to talk to Maxim about 100degC operation!
Keep well,
Will |
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