Losing Program when the electric goes out

[radal]

Hi,
 We have purchased several tm100md plcs in the past and they
work great. We sometimes lose electric and have to reload the
ladder program in the plc. Is there any way to save the program
so the ladder program doesn't have to be reloaded? I think when it happens we get a checksum error and it tells you to reload the program. Any input/suggestions would be greatly
appreciated.
Thanks,
Al

[FQ-ONG]

Basically, this will not happen on T100MD PLC unless the PLC was corrupted.

[radal]

Hi,
Can you tell me what would cause the PLC to become corrupted?

[support]

Do you mean everytime you turn off power to the PLC (even regular shut down) you would lose program? If that's the case check that the EEPROM jumper J2 is in the "Enable" position and not the "WP" (write protect) position.

If the program lost is occasional then you may want to check if you power supply behave well when power down. Sometime  a bad power supply may have surge voltages to the DC output when power failure occur which could corrupt the EEPROM. If that the case changing the power supply should eliminate the problem. Alos putting a diode and a capacitor at the power supply screw terminal should help to reduce fast voltage dip during power interruption that could cause the program to become corrupted. But be assured that only in very extreme situation would this problem occur. Tens of thousands of our PLCs used in industrial environment do not experience lost program even with daily power up/power down cycles.

[radal]

Hi,
 I checked the Write Protect jumper and they are in the enable
position. I am going to try buying new power supply's and
see if this helps.
Thanks - I'll let you know how I make out. It may be a while.

[benb2000]

I have 27 T100MD888+ units operating in a mobile application, getting its 12.0 VDC power from the Battery in the vehicle. The system has a "Mother Board" that supports the PLC and on the MB is a steering diode and then a 10,000 uF 35 VDC Aluminum Electrolytic cap supplying power to the PLC. In the Last 3 years I have replaced 6 ( Six ) M2017P EE-Proms because of the above mentioned issue. How much capaciatnce would you recommend?

has any one added any capacitance to the power rails adjacent to the EEProm? Say 10 uf Tantalum? Not knowing the part, I cannot look at the specs to see if it should be powered down slightly before or after the CPU.

[support]

Since your PLC Is powered from the 12V power source of the vehicle it could be affected by the load dump effect during vehicle start up or battery charging cycle.

You may like to try a "Load Dump protection diode" which is a kind of transient voltage suppressor - one possible part number is:  LDP24A which you can purchase from digikey.com

http://www.st.com/stonline/products/literature/ds/6116/ldp24a.pdf

Did you actually use a 10,000uF capacitor? We would like to caution that very large capacitor can discharge very high current if there is a short circuit at its output and that itself could damage sensitive electronic components. A 1000uF capacitor is usually sufficient to protect against voltage dip from turning on a large load.

[benb2000]

Thankyou for your information. I will purchase these "Load Dump protection diodes" , and install them on the power input to the PLC.

The "Motherboard" we use has another linear regulator on it, with appropriate reversed biased diodes for short circuit protection. It appears the T100MD888+ has these as well on the two power regulators at the input to the PLC.

In the 3 years of operation, we have had two op amp failures, and the six M2017P's. There are three Op amps per motherboard. to condition the Analog signals going into the PLC.
This is 2 Op amps out of 78 in use, versus six M2017P out of 26 PLC's.

I have had no other electronic failures of any other IC's on the PLC's, or motherboard.

It is also noted that there are no bypass caps ( .01uf or 0.1 uf ) near the M2017P, and only the 220 uf Aluminum Elctrolytics by the regulators. Alot of designers use tantalum and ceramic bypass caps for transient handling.

In the absence of other failures, it would seem that the M2017P is quite sensitive to something that the other components are not.

[support]

The load dump effect on a vehicle power can send more than 100V transient down the power line and the transient are probably too fast for the voltage regulator circuit to clamp down, hence the need to use a load dump clamping diode.  A DC-DC converter with surge protection will probably be the ideal setup.  Alternatively, get a DC-AC inverter to convert 12V to 110V, feed through a UPS and then back to a 24V regulated power supply - I know it sounds silly but I would imagine the intermediate components could effectively filter out any load dump transient. Even if this setup is untenable for mass production it could serve as a "control" to find out if transient was the real culprit that damages the M2017P.

There are thousands of M-series PLCs running 24/7 in standard factory environment and we didn't see any unusually high failure rate for the M2017P. But being a low voltage CMOS memory device it could be less robust than the logic ICs or the CPU (which uses mask  ROM).

[benb2000]

Checking with Digikey and Mouser for the Transient Voltage Suppression Diode LDP24A, In both vendors this non stock with a minimum of 690 or 490 parts at Mouser, or 800 and 1000 at Digikey. Do you have a source of small quantity of this Diode?

[support]

Try this part number:

1N6277AG  - Digikey part #1N6277AGOS-ND and they do sell 1 piece only.

Datasheet download:

http://www.onsemi.com/pub/Collateral/1N6267A-D.PDF

This one is rated for 18V. You could also get anything between 15 to 24V since the PLC will work in any of these range and regular vehicle alternator should produce < 13.5V during charging.

Looking at the spec sheet it seems to switch much faster than LDP24A.

[benb2000]

Thanks for the info.

[benb2000]

Hi,

I installed the 1.5KE24A transient suppression diodes across the power leads comining into the unit. This is upstream of the steering diode feeding the circuitry.

The remedy is not 100%, I have had units returned from the field, after the diode has been installed, where the M2017P has been corrupted, some to the point of not being able to re-program.

I think your firm should develop a special power conditioner module, to allow relable use of a T100MD888+ in an Automotive application.

Our dealer, DCI Inc. in Calgary Canada,  pointed us to a DC/DC converter that they have been trying, we purchased a few, and are trying them as well, so far no field results. Lab tests have been positive.
We are also going to try the DC UPS from http://www.powerstream.com/DC-UPS-1212.htm and add a Sealed Lead Acid gell cell to the system.

My biggest problem with all of this is that the only item to fail is the M2017P.