AMC7135 Specs Inside **UPDATE**

[Drewfus2101]

1050mA version:

1400mA version:

Pretty good boards, as long as your in they're small voltage range. DX recommends that you stay within 3.6V to 4.5V. I read that is because between 4.6V to 6.0V (which it can take up to 6.0V) it gets very hot. In my testing I used a small fan to keep the board cool so this did not affect me.

These are a great alternative to resistors, even though resistors are cheaper. The best thing to do here is order 20 of the 1400mA version and you can remove each of the black AMC boards and each one you remove will cut down the output current by 350mA. I tested this and it does work.

Where these boards beat resistors is that these give you a semi-regulated output. If you use resistors and alkalines (for example) the flashlight will never be brighter than when you first fire it up. After that, the batteries will start to dim. If you chose your resistor based on the fresh battery voltage, as the batteries start to drain, your output will drop. With these, as long as your voltage stays above about 4.0V you get the full output. The 700mA version should need a lower voltage and the 350mA an even lower voltage. So that semi-regulation is worth the extra money to me. I can't tell you how much time and headache direct drive / resistors / alkalines have caused me.

I definitely love a good boost/buck convertor more than these, but these things are not bad little boards. I thought others could benefit from these numbers.

 

[TorchBoy]

Re: AMC7135 Specs Inside

Nice results. I'd be more interested in graphs of output current for input voltage, though. (I don't quite see the point of efficiency graphs for linear regulators.)

On the subject of them being linear regulators, how did you get more current out that current in?

 

[Drewfus2101]

Re: AMC7135 Specs Inside

I'd say that the current in and current out are probably equal its just that my accuracy in measuring them is slightly off.

Charts as requested:

 

[TorchBoy]

Re: AMC7135 Specs Inside

Wow, awesome! That shows just when the thing drops out of regulation. Now, why wouldn't it be completely flat when in regulation? Temperature effects in the AMC7135s?

 

[Drewfus2101]

Re: AMC7135 Specs Inside

Wow, awesome! That shows just when the thing drops out of regulation. Now, why wouldn't it be completely flat when in regulation? Temperature effects in the AMC7135s?

Not this time, at least I doubt it anyways. I had a small 12V fan running off of a separate power source an inch from the board running full out the whole time. It was moving more than enough air to keep the thing cool and the board was very cool to the touch when I picked it up as soon as I turned off the power. But I wouldn't run the same test without the fan, at least not up to 6V and I probably won't use these boards up to 6V without some testing first.

 

[ktronik]

Re: AMC7135 Specs Inside

Great info...

I did a test by mistake

I had a 3d m@g with some AMC's in... by mistake I put 3/ 3 AA carriers, way over voltage spec...

The light worked fine, until the AMC's heated up enough to melt the solder holding them on the board & slid off...

After re-solding them back on they still seem to work ok on normal voltage.

I would say they are pretty tough.

with in the right voltage range, they a great cheap circuit to work with...

Great for 4 nimh's, as by the time they are drained (3.2v min) the AMC's are draining very little, a great low batt warning.


K

 

[TorchBoy]

Re: AMC7135 Specs Inside

I knew they were tough, but that's amazing. You're talking 180-190 °C. It sounds like a very easy way to get them off the board.

I thought the thermal protection cut in at 150 °C. :thinking:

On a multiple AMC7135 board and too many volts they'll presumeably starting blinking, but they'll all be blinking out of sync with each other. Would it even be noticeable?

 

[ktronik]

Re: AMC7135 Specs Inside

I think you may be right... they started blinking a bit, so I tapped the light head...thats when the AMC's slid off the board...

K

 

[mike2g]

Re: AMC7135 Specs Inside

I've been thinking about using these boards in a single li-ion powered light but am concerned with the loss drop in output current after the voltage drops below 4 volts. The reason I like these boards is that the efficiency of the boards is above 90% for most of the life of a single li-ion. However, the output doesn't seem to be very well regulated. According to this, for the case of the 1400ma version, the output current can be expected to drop substantially, 1.28A -> 0.85A, after the battery capacity has dropped to 80% of its' capacity. Basically, a 1/3 drop in out put after a 1/5 drop in battery capacity.

It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this?

Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf. For example it has been rumored that the Q5s have relatively high Vf, so would using a lower Vf emitter such as a SSC P4 shift the graph and increase the range where the output current could be regulated?

Thanks for putting this together, it's been very helpful!

 

[SnowplowTortoise]

Re: AMC7135 Specs Inside

Great post! Thanks for passing on the info. 60% efficiency at 6V is pretty scary.

Craig

 

[CampingLED]

Re: AMC7135 Specs Inside

Great review. Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s. Will appreciate it if you could do a simple test when the diodes are shorted out.

 

[Mr Happy]

Re: AMC7135 Specs Inside

I've been thinking about using these boards in a single li-ion powered light but am concerned with the loss drop in output current after the voltage drops below 4 volts.

This is unfortunately to be expected. The board is apparently a buck regulator, which means it can reduce the battery voltage but cannot increase it. Regulators of this type also need an extra margin of input voltage over output voltage to operate properly. In this case that margin is only about 0.3 V, so I think it's doing pretty well.

The reason I like these boards is that the efficiency of the boards is above 90% for most of the life of a single li-ion. However, the output doesn't seem to be very well regulated. According to this, for the case of the 1400ma version, the output current can be expected to drop substantially, 1.28A -> 0.85A, after the battery capacity has dropped to 80% of its' capacity. Basically, a 1/3 drop in out put after a 1/5 drop in battery capacity.

When the voltage drops below 4 volts the unit has dropped out of regulation due to insufficient input voltage. To obtain good results, the battery used should provide more than 4 volts until fully discharged. [Edit: For the particular LED tested in this case.]

It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this?

Not inexpensively, no. If you look at the voltage in vs. voltage out tables, you can see how the unit would have to boost the voltage to achieve what you wish, and this would be extra circuitry.

Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf. For example it has been rumored that the Q5s have relatively high Vf, so would using a lower Vf emitter such as a SSC P4 shift the graph and increase the range where the output current could be regulated?

I think it would help, yes. Anything that lowers the required output voltage would extend the range of regulation.

 

[Marduke]

Re: AMC7135 Specs Inside

Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?

 

[Drewfus2101]

Re: AMC7135 Specs Inside

Great review. Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s. Will appreciate it if you could do a simple test when the diodes are shorted out.

Wow, I almost forgot about that trick. I bookmarked some info about that, but forgot to try that when I was running this test. I should have a night this week to run more tests and I'll add this to my list.

 

[Drewfus2101]

Re: AMC7135 Specs Inside

Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?

I'm pretty sure they can not. They are "buck" type boards so they can only reduce the voltage in. Notice how the current in and current out are practically identical (not counting multimeter accuracy error)? It would be pretty much the same as direct driving. The only benefit of using two of these (assuming that worked) was to buck the voltage down. But you can't go higher than 6.0V with these and DX recommends no higher than 4.5V due to heat.

I'm sure someone with a P7 will try it and it might just work, but I can't figure out how and it won't be efficient.

 

[Drewfus2101]

Re: AMC7135 Specs Inside

I think it would help, yes. Anything that lowers the required output voltage would extend the range of regulation.

I'll try and repeat the test with an SSC Z-power. Its the only other emitter I have that is star mounted and will work with my setup. I'll double check the emitter first and make sure it has a lower Vf too.

 

[TorchBoy]

Re: AMC7135 Specs Inside

It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this?

Use a lower voltage (Vf) LED.

Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf.

In the way that you want. The AMC7135 needs at least 2.7V and white LEDs have a Vf above that, so you'll be fine.

Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s.

Let's see... The voltage drop across one of those diodes will be ~0.6V so if your input voltage is less than 3.3V it might make a difference, since the AMC7135 needs 2.7V to stay in regulation, but would your LED Vf be that low? Quite possibly - I've got one Cree with a Vf of 3.3V at 1A. Drewfus, it wouldn't have made any difference to your test, because your operating voltages were higher than that.

The board is apparently a buck regulator, which means it can reduce the battery voltage but cannot increase it.

No - it's a linear regulator - and yes respectively.

When the voltage drops below 4.0 volts the unit has dropped out of regulation due to insufficient input voltage. To obtain good results, the battery used should provide more than 4.0 volts until fully discharged.

That will depend on what the LED wants. For the particular LED tested, with a reasonably high Vf of 3.7V @ 1A, you do need at least 4V.

Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?

Yes, not a problem. Someone recently even figured out how to connect a multimode board to a single mode multi-AMC7135 board to get lots of current and multiple modes. The efficiency, Drewfus, comes from running these things with a Vin a little higher than the Vf of the LED. Whether that's 3.3V for a low Vf Cree P4 or 4.2V for a SSC P7 doesn't matter.

 

[TorchBoy]

Re: AMC7135 Specs Inside

Here we go - multimode driver for P7. It has also has a diagram of how to connect two 4xAMC7135 boards in parallel. Easy.

 

[Supernam]

Re: AMC7135 Specs Inside

Darn, I found this post a little too late. I wanted to use this for 3D NiMH's, but I they provide probably a max total of 4v rested off the charger. I'm thinking the best would be 4D NiMH's or 3D Alkalines. Alkalines shouldn't sag much at only 1A, so I'm thinking I'd get some ridiculously long runtime right?

I guess I can't complain since they're less than $2 each!

 

[TorchBoy]

Re: AMC7135 Specs Inside

Supernam, if you're going with alkalines I'd definitely recommend 4 instead of 3. Their voltage really doesn't hold up and most of their life is with a lower voltage than would do the job if you only had 3.

With NiMH, it would depend what the Vf of your LED is and when you wanted the thing to drop out of regulation. Drewfus' test above showed his LED needed 4V for the board to stay in regulation, so 4 NiMH cells would probably work better in that situation, and drop out of regulation at a loaded 1V per cell. Note though that the board might get quite hot when the NiMH cells are freshly charged.