TLE5205-2 Problems

[schmidtbag]

I have a couple of E30-400 Amplfow motors, which demand up to 24V and 29A. The thing about these motors, though, is they require a mechanical speed reducer to operate them safely at such a wattage. I figure that you can safely operate these motors (without a speed reducer) at 12V 20A. I intend to drive these motors with car batteries but I'd rather not have them operate much beyond 20A. So to reduce power consumption, I got the TLE5205-2 which can drive motors at 12V 5A. I figured if that's too weak, I can just put 2 of them in parallel.

The problem is, the motors demand so much current that the TLE5205-2 triggers its overcurrent protector. I'm not that great with electronics, so my idea was to either somehow make the motors less demanding or to reduce the incoming amperage to the TLE5205-2 to maybe 7A. I'm not sure how to do either. Considering the motors are allowed to operate at 12V and the TLE5205-2 supports up to 40V, I wouldn't mind converting the amperage to voltage, if that helps, but I'm not sure how to do that either.

 

[(*steve*)]

Post some links to these devices.

If you're using a 5A controller to try to control a 20A motor, are you surprised that they trip out when the motor demands 20A?

 

[john monks]

Unless the TEL5205-2's are identical you might have a problem placing two in parallel.
I wouldn't do it.
Have you considered using some insulated gate bipolar transistors?
The bad thing is that you have 266 amps of stall current in your motor.
Have you considered using a smaller motor?

 

[schmidtbag]

Well I figured these ICs would work similarly to other H-bridges where they just simply output up to whatever amperage they offer whether the device demands more or not. In other words, if I had a 1A light bulb and applied 500mA, I'd expect it to shine at half brightness but shine nonetheless. The motors spin fine using the 5v 20A from a computer PSU, so clearly they can operate at a lower wattage. Like i said, i don't know much about electronics, i figured this IC would just simply output 5A regardless of demand, assuming the power source could supply it.

The TLE5205s are all identical, I got a pack of them of the same manufacturer. Once again my poor electronics knowledge is kicking in, where I'm not sure how bipolar transistors work, or what the significance of stall current is. Is stall current the amount of current needed to get the motors stopped to moving?

I'm sorry if these seem like stupid questions, I'm more of a software guy.

 

[john monks]

Stall current is the amount of current the motor draws when the shaft is locked so it will not turn. This may not be a big issue with you but when you first apply power to the motor the shaft is not turning and you may approach stall current before the motor starts turning. I thought this may be a good approximation of your worse case scenario for current. I happened to notice "stall current" on the datasheet.

I don't know if you can use two TEL5205-2's in parallel.

It seems to me that the simplest solution is to lower the supply current.
I assume the stall current will go down with the supply voltage.

 

[schmidtbag]

Stall current is the amount of current the motor draws when the shaft is locked so it will not turn. This may not be a big issue with you but when you first apply power to the motor the shaft is not turning and you may approach stall current before the motor starts turning. I thought this may be a good approximation of your worse case scenario for current. I happened to notice "stall current" on the datasheet.

I don't know if you can use two TEL5205-2's in parallel.

It seems to me that the simplest solution is to lower the supply current.
I assume the stall current will go down with the supply voltage.

Thanks for the clarification. But as for lowering the supply current - that's one of the solutions i thought of myself and was asking how to do it. I'm temporarily using a computer PSU at 12v, which supplies 20A. The problem, though (which strangely doesn't occur with the 5v wire) is if I wire it directly to a motor, the PSU too has an overcurrent protector and shuts off before it can power the motors. This doesnt apply to smaller motors. This is why I purchased the TLE5205-2, because I expected that the IC would only intake 5A, which wouldn't overload both the PSU and the motors. But as stated before, the IC also wants to complain about overload.

So, how can I reduce the current going to the IC? If my memory serves me correctly, one way to do this is to increase voltage. Since these motors can operate at up to 24v, I wouldn't mind using that as a solution to reduce the supply current but I'm not sure what can do that.

 

[john monks]

Increasing the voltage will increase the current drawn.
The only thing I can think of is to use a very large dropping resistor in series with the motor. Something like an electric space heater. They are typically about 10 ohms.

The only practical solution I can think of is to a smaller motor.

Have you considered using a 12 volt battery charger?

 

[schmidtbag]

Increasing the voltage will increase the current drawn.
The only thing I can think of is to use a very large dropping resistor in series with the motor. Something like an electric space heater. They are typically about 10 ohms.

The only practical solution I can think of is to a smaller motor.

Have you considered using a 12 volt battery charger?

Well i meant convert the excess amps into volts, unless that doesnt change your point. Is the space heater really necessary though? Wouldn't that still trigger the PSU overload protector? I just find it hard to believe there's not a more reasonable solution. I'm not against getting a different IC but I haven't found many that were either affordable or didn't allow 40A for an output.

Personally I don't understand why the TlE5205-2 even has the protector, where IIRC many other H-bridges choose to shut off from heat, which makes a lot more sense. If it can't take in more than 5A, I don't see why it matters if the output device demands more, it makes no sense to me aside from the temperature problem. The way I see it is like this:
Microcontrollers can take 30A being pushed into them at 5V and not overheat, yet their digital pins still only output no more than 100mA. If you connect a device that demands more power, the MCU still runs fine, the device just doesn't power properly. I don't see why that doesn't apply here and why the same thing can't be accomplished but at a higher voltage.

 

[schmidtbag]

So I found this and was wondering if you think it would help:
http://www.ebay.com/itm/DC-DC-4A-4-...769?pt=LH_DefaultDomain_0&hash=item2323b3af69

I was thinking of using this to convert the power source of 12V 20A (or higher amperage with the battery) to 24V 4A. Do you think this is a good idea, or do you suspect this product would also start whining about too much current draw? While the output current is lower than I prefer, 96W is still better than the 60W I was expecting before. Keep in mind the motors were spinning just fine at 100W with the 5V source from the computer PSU.

 

[john monks]

From the specifications I looks at the motor draws a certain amount of current when you apply a certain voltage. So if your chip starts outputting too much current it shuts itself down to prevent itself from being destroyed.
So what you need to do is to find a way of limiting the current.
I suggested using a space heater as a resistor because the resistor must be able to dissipate many watts, much more than the common resistors found in a parts house. At least you would be able to see if the rest of the circuit is functioning correctly.
The bad news is you need to come up with a motor driver that can handle the amperage or select a smaller motor.
Maybe a relay circuit would work.

 

[schmidtbag]

From the specifications I looks at the motor draws a certain amount of current when you apply a certain voltage. So if your chip starts outputting too much current it shuts itself down to prevent itself from being destroyed.
So what you need to do is to find a way of limiting the current.
I suggested using a space heater as a resistor because the resistor must be able to dissipate many watts, much more than the common resistors found in a parts house. At least you would be able to see if the rest of the circuit is functioning correctly.
The bad news is you need to come up with a motor driver that can handle the amperage or select a smaller motor.
Maybe a relay circuit would work.

Ok, thanks a lot i appreciate your patience and detailed clarification. I'll see what I can do.

EDIT:
I realized the link I showed before is far from good enough. I found another product that I think ought to do the job perfectly:
http://www.ebay.com/itm/120W-DC-Con...713?pt=LH_DefaultDomain_0&hash=item27cc2c0dc1