Current/voltage limiting circuit 3

[gobears1]

I need to protect a 24 VDC system fed from a large mining haul truck for current/voltage spikes.

It's spec would range from 18-32 volts and .18 to .75 Amps.

Can anyone help me with this?

 

[OperaHouse]

Do you mean that the load can tolerate the voltage going to 18V or do you need to also boost the voltage in a drop out condition?

The simplest way (although not exotic) is to have a smaller seperate battery that operates the device and is charged through a diode and small 5 ohm resistor. Two small 12V gell cell batteries don't take up much room.

 

[IRstuff]

VICOR (and others) makes an Input Attenuation Module (IAM) that provides filtering, EMI suppression and polarity reversal

TTFN

 

[gobears1]

Thank you for the reply OperaHouse. I forgot to add a vital piece of the pie. It needs to operate at temperatures as low as -40 F. So, if possible I would like to stay away from any additional batteries as this circuit has to be mounted outside of the heated cab of the vehicle.

 

[waross]

I imagine the 18 volts is during engine cranking and the 32 volts is the charging volyage.
It's pretty hard to get a voltage spike from a pair of 8D or larger batteries.
Have you considered connecting your equipment closer to the batteries?
The voltage surges are most likely generated in the supply wiring rather than originating from the battery.
Take a look at what equipment shares the supply conductors with your sensitive circuit.
Don't forget the ground circuit. A bad ground can do all sorts of interesting things.
If your circuit is grounded to the chassis rather than with a wire to a designated ground point that may be your problem.
yours

 

[itsmoked]

I don't understand are you designing something and need to know about load dump protected regulators?:

http://cache.national.com/ds/LM/LM2931.pdf

Or some add on gizmo that goes between some aftermarket thing and the vehicle?

If you need to keep a 24V aftermarket device happy at 18V then you need special equipment.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[nbucska]

The simplest is a switching DC-DC converter.
The most expensive part is a PC board.
Is it supposed to be constantly ON ?
How many do you need ?

 

[Comcokid]

The way I read this is that you have a device that will operate from 18 to 32 volts, pulls 180 to 750 mA, and you want to operate it from a 24 volt vehicle system. Is this correct?

If so, then a voltage regulator (designed for vehicular systems as itsmoked suggested) and/or MOV (rated for 24 volt vehicular system) on the input may be all you need.

However, from experience I know that in some heavy industrial vehicular environments - particular near mines that vehicles can be jump-started from arc-welders or 80 volt DC mining carts (fork lifts, etc). Equipment handlers will resort to many 'unusual procedures' to keep schedule when batteries are dead and it's cold enough to gel diesel. Such situations are outside of normal "load-dump" considerations. If this is a possibility, then you need a transistor/zener circuit that opens when a certain voltage is exceeded, or a protection module. By protection module, I mean that someone, somewhere, probably had a module designed to protect devices used on an industrial vehicle - try a google search or talk to the equipment supplier for suggestions.