Fyi: G540 contains magic smoke.

[Vestus]

The previous owner had the output hooked to an automotive relay (for headlights) and it was limping when I bought his kit.

If you're going to use the output to control your router, I strongly suggest getting a relay from CNC4pc or the like instead of going the 'cheap' route.

[alan_3301]

The previous owner had the output hooked to an automotive relay (for headlights) and it was limping when I bought his kit.

If you're going to use the output to control your router, I strongly suggest getting a relay from CNC4pc or the like instead of going the 'cheap' route.

that looks like my old g540. The manual made it seem like power supply voltage was ok for operating relay coils. Mine worked great for about 6 months at 48volts, then smoked one output ciruit, then the other soon after. I ended up jumpering the parallel port pin to the output pin, then using a transistor to operate a relay, running off of a 12 volt power supply. I'm sure a regular auto relay will work just fine, as long as it has its own 12 volts supply.

[jm82792]

I bought a $40 Opto22 relay that has a lifetime warranty, that are rigorously tested and such from ebay as NOS for $12. 3 to 10 volts for control, it controls 120VAC at 10 amps.
Think of it, no inductive kickback and no worries

[Bob La Londe]

Not sure what tou guys mean. I am running 48VDC relays from Altronix on bith of my small machines for switching 110 to my routers and coolant pumps. They have been working fine for quite some time.

[CarveOne]

In the old days of dinosaurs, alchemy, and analog electronics with actual wires on the components (how quaint it all seems now) we used to put a reverse biased silicon diode of the empirically calculated voltage and current rating across the relay coil to shunt the reverse voltage spike from magnetic field collapse. Using 25 "digital components" to do the same function is SO much better for business.

[Bob La Londe]

In the old days of dinosaurs, alchemy, and analog electronics with actual wires on the components (how quaint it all seems now) we used to put a reverse biased silicon diode of the empirically calculated voltage and current rating across the relay coil to shunt the reverse voltage spike from magnetic field collapse. Using 25 "digital components" to do the same function is SO much better for business.

I use diodes on things like maglocks and electric strikes all the time to reduce problems with relay contact welding. The relay itself should not cause a problem with its control but if it does there are some nice optically triggered relays that only draw about 1.2 mills on the trigger input. I don't think I have ever had one fail (and I have been using them for almost 20 years) in continuous duty applications like this where they are being activated multiple times per day every day for years on end. They are not super expensive compared to other quality relays either. Yes, they cost a lot compared to the junk you find at Rat Shack, but...

Some applications spec MOVs instead of diodes. I think the idea is that it can provide a voltage drain on both start up and shut down as opposed to a diode.

[TechGuy5002]

When the coil power is dropped it causes a high voltage spike that can be up to about 10 times the input voltage. This can exceed the Mosfet (or bipolar transistor) voltage rating causing it to fail. Typically a reverse recovery diode is placed across the relay coil inputs (in opposite polarity - Cathode to Vin and Anode to Gnd). The diode clamps the reverse recovery inductor spike and preserving the transistor.

Some relay sockets have built in diodes to clamp the spikes and thats probably why some people have no issues while others get their controllers fried.

[Al_The_Man]

MOV's are typically used on AC circuits, the problem with this device is it is progressive, the resistance decreases with an increase in voltage, it is bi-directional in operation, but tends to degrade when subjected to repeated high voltage conditions.
They can fail open because of this without any warning or indication.
As opposed to the diode on a DC coil where it conducts immediately as soon as it is forward biased.
By experience I have found RC snubbers more effective than MOV's on AC coils and across AC supply lines for suppression purposes.
Incidentally the BEMF from some DC devices, can reach in far in excess of 10x the supply, depending on the energy stored, enough to give a fairly nasty shock.
Al.

[Mariss Freimanis]

Too bad about your G540 motherboard; the load current was big enough to char the board but not big enough to blow the output MOSFET immediately. That would have resulted in repairable damage.

Couple points:

1) A 12VDC relay coil draws 4 times its rated current at 48V. Do Ohm's Law on the coil before you use it with the G540. Measure the coil resistance with a multimeter; don't use it if it's not rated at 48VDC or it's less than 48 Ohms when using a 48V supply.

A 12VDC coil is going to draw 4 times its rated current and generate 16 times the rated heat in the coil. What probably happened is the coil overheated, shorted out and blew out the G540 output driver.

2) The G540 has diodes on the outputs and handles inductive fly-back voltages.

Mariss

[Vestus]

Good to know. I'm surprised and disappointed that Gecko didn't put replaceable fuses on these.

I'm not sure what he did to start the downhill slide, but he ended up rigging a doohicky with more relays and diodes to a 12v/2A supply to compensate and keep it working until he sold it to me. After I bought it, it lasted three weeks of minimal 'howDoIWorkThisThing' use and puffed out.

My replacement now uses a 5v/.5A USB supply and a relay from CNC4PC that works like a champ. I'm pretty sure that setup won't blow this Gecko too. On the upside, I can run my laser cross-hair off of it too.

[Bob La Londe]

Altronix: a leading manufacturer of electronics and high technology components

This relay switches off the G540 perfectly when using a 48VDC power supply. Its has DPDT form C contacts. It only draws 20 mills to trigger, and you can switch 10 amps on the contacts all day long with no issues. (10 on each side) In fact I have one running an 11 amp router, and a low current coolant pump. That happens to be the machine I use all the time.

They also offer a 12V and a 24V version. Similar specs.

You should be able to find them retail for around $20 +/-.

[Mariss Freimanis]

Vestus,

What you mention is a core goal (reliability and fault tolerance) when designing a new product. Another, but conflicting, core goal is product value (high performance at a low price).

Every designer has to find the best mix of these opposing goals. Over-emphasize robustness and you design a product that is too expensive to market. Over-emphasize value and you design a product that is too fragile. Do either without a sense of balance and the design becomes a marketplace failure.

A way of ensuring reliability is to have published specifications for the product. Specifications are a guarantee the product will work as claimed so long as the published parameters aren't exceeded. It is the user's responsibility to not apply conditions that exceed the specification limits; had the applied load met specification, the G540 would still be healthy.

We at Geckodrive also realize that user errors happen and the result can be a dead drive. The user is usually out some money even though the error wasn't intentional or due to negligence. It leaves me with a sick feeling in the pit of my stomach when it happens to me.

For that reason Geckodrive has as policy a "One time, stuff happens deal". Send the crispy G540 critter back to us. We will repair or replace it one time only for free no matter what was done to it and it even includes free return shipping. The drives are probably OK but from the picture the motherboard is beyond resuscitation. It will be replaced with a brand-new, fresh volunteer.

Your G540 will be tested and returned to a factory-new condition. The drives will be washed to remove the corrosive "magic smoke" they are covered with in the picture. So will the G540 package cover. Our policy is everyone deserves one "do-over'".

Mariss