Hi,
I removed the A23 12V battery in my NICE remote control and connect it direct to my car's 12V supply via the fuse box.
It worked for the last 2 weeks but today, it died. The red indicator light is still blinking though but the gate will not open.
I suspect that the alternator may have supplied maybe 14 to 15 plus volts and killed some components which I have no idea how to
trouble-shoot. Could anyone give me some ideas where to start? Thank you.

 

That's a difficult device to troubleshoot. Don't have any good suggestions.
Perhaps someone else has a idea on that.

 

I don't see a schematic so I don't know if you've included protection against higher voltages hitting your circuit. Maybe you can add a simple modification which ensures that the highest voltage applied to the components is 13 volts. A circuit containing a zener diode would suffice.

 

Unfortunately the most likely components to be fried by over-voltage are the multi-legged processor IC and the radio module in the can. I doubt it's economic to try replacing either of those, even if you could get them .

 

Why would you go to all the trouble to connect to remote directly to you car's battery just to save the occasional replacement of the battery?
Are the batteries that expensive?

 

That transistor closest to the SAW resinator probably has, or had, a very low breakdown voltage. I would check for a collector-to-emitter short.

 

The automotive environment is quite nasty: See https://www.google.com/url?sa=t&rct...h7JGwMJ1lI2sThXcw&sig2=XhuPqzr2MDE1dV1JTEBF9Q

The "surge stopper" IC;s from Linear technology is exceptional.

At the very least, you have to clamp the + and - voltages. that battery is rated for 12 V and the car's electrical system is at least 13.8 V.

The datasheet for the NDR433T is easy to get a hold of.

You can try this trick: Short the battery terminals (no battery) for at least a minute.

 

I'm not sure what the trick is but it worked! Thank you.
By the way, I know little about electronics so could you kindly help me understand what is going on and how should I go about getting a stable 12V from my car battery. Would a LM2940 12V 1A low dropout regulator be the solution or just simply a 12V Zener? Thank you so much. By the way, has any permanent damage been done now that its working?

 

You can try this trick: Short the battery terminals (no battery) for at least a minute.

Nice one, KISS. What's the theory behind that?

 

It probably surprised the daylights out of you, didn't it?

Permanent damage - probably not. I've used this successfully many times. There is a reason why it works.

The LDO is not a bad idea, but you also need to protect the system with an 18 V TVS diode such as http://www.digikey.com/product-detail/en/littelfuse-inc/SR05-02CTG/F6188CT-ND/4251857 and a reverse biased diode for negative voltages. Shockley is probably better.

The surge stopper http://www.linear.com/products/Surge_Stopper,_Overvoltage_*_Overcurrent_Protection products are better combined with a regulator.

 

In CMOS devices it's possible to trap charge with "no way out". The charge can "leak out" over a long time. The short enhances the ability to leak out the charge. Hence, it's non-destructive. Some transient, most likely caused the charge accumulation. I MAY have read it in the book "Intuitive IC electronics". I did take a solid state physics course.

I fixed an automotive clock (quit after a jump), an HP calculator stuck in commas for decimal points and a bike computer that was drug across a static generating mat. The latter two were not mine.

 

It probably surprised the daylights out of you, didn't it?

Permanent damage - probably not. I've used this successfully many times. There is a reason why it works.

The LDO is not a bad idea, but you also need to protect the system with an 18 V TVS diode such as http://www.digikey.com/product-detail/en/littelfuse-inc/SR05-02CTG/F6188CT-ND/4251857 and a reverse biased diode for negative voltages. Shockley is probably better.

The surge stopper http://www.linear.com/products/Surge_Stopper,_Overvoltage_*_Overcurrent_Protection products are better combined with a regulator.

Yes, it was a very pleasant surprise I must say!
Honestly speaking, given very little that I know, I also don't understand the details. Are there 2 possible solutions in the above?
1. Use LDO with 18V TVS diode and reverse biased diode or
2. Use surge stopper (any part number? I'm lost) with regulator (which regulator; LDO?)

Thanks for your guidance and patience and thanks to all who replied to my post.

 

If it was mine I would just put a 2200 uF capacitor where the battery was with a 12-volt Zener diode across that and feed the whole thing through a 500 - 1000 ohm resistor.

Simple but effective voltage and spike protection.

 

Transient suppression can be done with the TVS and a reverse biased diode. The TVS diode is basically a fast diode that can handle a spike of a pretty high intensity. 18 V is nice voltage to clamp at because it would be passive if the alternator failed. The other diode basically suppresses at <0.6 V depending on the selected part number.

The surge stopper is "better"in my opinion. I didn't go selecting parts. Some of the packages are hard to work with.

You don't know the absolute maximum voltage for the parts used, so stick to 12 V as a regulator. The 12 V regulator is required in both cases.

The Zener regulator proposed by tcmtech is better than nothing. It is missing the reverse biased diode for negative spike protection.

So it's more like good, better, best. www.proto-advantage.com will mount and purchase a digikey part on a thru-hole adapter for you. You select the adapter and the digikey part.

 

Thank you. I will take a look at proto-advantage

 

alec:

It also worked on a Carrier thermostat where thee backlight would basically stay on continuously and some buttons didn't like to work. I did that one a bit differently. I just turned off the furnace/AC for about 2 weeks and I did try to activate the buttons on a turned-off unit. I then added a bidirectional TVS at the furnace (R & C) for 24 VAC and it's been working for 2 years+. A replacement thermostat is like $450.00+ USD. Control boards are also expensive, so the TVS makes a lot of sense.

The furnace motor was interfering with X-10 modules, so that was fixed with a power line filter at the furnace.

==

The car clock problem was "No display".

 

If it was mine I would just put a 2200 uF capacitor where the battery was with a 12-volt Zener diode across that and feed the whole thing through a 500 - 1000 ohm resistor.

Simple but effective voltage and spike protection.

Thanks. Am I correct it should be like this?

Is that cap an electrolytic type and would 20V be ok?
I think the unit draws 15mA max, what would be an appropriate power rating for the zener?
Don't mind if I ask are all the polarities indicated correct?
Is the resistor to limit the current to the zener and will it also cause the voltage to drop across the capacitor instead of the getting the entire source voltage?
Hypothetically, what if the voltage drops to 12V?

 

That's what I am thinking.

At a good 12.6 volt state of charge for the vehicle battery with the engine off the 500 ohm load going into the 12 volt Zener diode would give you at most a parasitic drain of ~ 1 ma. If you battery is below 12 volts then obviously a 0 drain.

As for voltage drop how low does your battery voltage go before the unit stops transmitting?

At a ~15 ma draw when transmitting the 2200 uf capacitor should easily give you several seconds of transmit time before its charge voltage drops too low. If not then the resistor could be reduced to a 100 - 200 ohm unit and a larger capacitor could be put in.

The Zener regulator proposed by tcmtech is better than nothing. It is missing the reverse biased diode for negative spike protection.

How big of negative spike are you planning for that will pass through a 500 ohm resistor to drain a large capacitor and overdrive the Zener diode in forward conduction mode to the point of destroying the transmitter?

 

If your current limiting the spike then your right. Probably OK.

Littlefuse says around -100 V for 200 mS at each turn off. Significant? IDK.

ESD events are infrequent and random an > 15 kV and < 50 nS.

Pick how important it is. The TVS can still be used with the Zener regulator too.

 

The zener should also provide some protection against negative transients, since it would then be forward biased. A Schottky would probably be better though.