Maximum voltage to the Bot board?

[rryerson]

Hello,
I just saw in the Atom Pro manual that the maximum VIN voltage is 12V. My question is can the Bot board handle 12V input safely? I won’t be drawing more than 200 mAh from the board. I using a few SRF05 pings and a couple of sharp IR detectors… The reason I am asking is I am running 12V motors and I don’t want to use a seperate battery for the bot board. I am also trying to avoid using a voltage limiter to step the 12V down to 9V or so.

Thanks for time
Richard

[kroony]

The power for your sensors would come from the Mini-ABB, not the Atom Pro. The regulator on the Atom is only small and would not ba able to supply much current, so it is only used for the components on the stamp.

The Mini-ABB (I assume you are using this) manual says that the regulator on board can handle 500mA from a 9v source.

@Mini-ABB Manual

The Low Dropout regulator will provide 5vdc out with as little as 5.5vdc
coming in. This is important when operating your robot from a battery. It can
accept a maximumof 9vdc in. The regulator is rated for 500mA, but we are
de-rating it to 250mA to prevent the regulator from getting too hot.

Hope this helps. Sorry for the bad news.

[rryerson]

@Kroony

The power for your sensors would come from the Mini-ABB, not the Atom Pro. The regulator on the Atom is only small and would not ba able to supply much current, so it is only used for the components on the stamp.

The Mini-ABB (I assume you are using this) manual says that the regulator on board can handle 500mA from a 9v source.

@Mini-ABB Manual

The Low Dropout regulator will provide 5vdc out with as little as 5.5vdc
coming in. This is important when operating your robot from a battery. It can
accept a maximumof 9vdc in. The regulator is rated for 500mA, but we are
de-rating it to 250mA to prevent the regulator from getting too hot.

Hope this helps. Sorry for the bad news.

Yes, I got that… the mAh draw won’t be the issue. I won’t be drawing much from the board. What I am concerned about is the voltage being 3V over the specified max of 9V… can the Mini-ABB regulator handle 12Vs?

Thanks, though.
Richard

[rryerson]

@Kroony

The power for your sensors would come from the Mini-ABB, not the Atom Pro. The regulator on the Atom is only small and would not ba able to supply much current, so it is only used for the components on the stamp.

The Mini-ABB (I assume you are using this) manual says that the regulator on board can handle 500mA from a 9v source.

@Mini-ABB Manual

The Low Dropout regulator will provide 5vdc out with as little as 5.5vdc
coming in. This is important when operating your robot from a battery. It can
accept a maximumof 9vdc in. The regulator is rated for 500mA, but we are
de-rating it to 250mA to prevent the regulator from getting too hot.

Hope this helps. Sorry for the bad news.

… further… according to this web page for the regulator on the Mini-ABB (google the model # on the back of the regulator on my bot Board) national.com/pf/LM/LM2937.html. The max input voltage is 26Vs. So if the regulator and the Atom Pro can handle 12V… what else on the bot board do I need to worry about over volting?

Thanks again

[kroony]

You might have to just give it a go and keep an eye on the temperature of the regulator.
I don’t know what regulator the Mini-ABB uses. Can you post the component number, then we could have a look at the data sheet. It should give a better idea of what would be ok.
Also, how many sensors are you using? The sharp sensors draw a reasonable current, and the ultrasonics can when they are transmiting their pulses. The more info the better.

Edit: Just looked at the data sheet. The 12v should be fine, but I would still recomend that you keep an eye on the temerature of the regulator. It has short circuit and thermal overload protection, so you shouldn’t wreck anything.

[sn96]

12v will work but not recommended. It will shorten the life of the regulator. If I remember corectly, Jim said 7.5v-7.8v is fine for every day use. The regulator used on the bot board LM sells in the component section.

[eddieb]

@rryerson

… further… according to this web page for the regulator on the Mini-ABB (google the model # on the back of the regulator on my bot Board) national.com/pf/LM/LM2937.html. The max input voltage is 26Vs. So if the regulator and the Atom Pro can handle 12V… what else on the bot board do I need to worry about over volting?

I think your limiting factor will be heat dissipation from the regulator as it has no heatsink per-se. 12V to 5V is a 7V drop and your estimated current is 0.2A so the regulator would be dissipating about 1.4 watts. That is pretty hefty for no heatsink and may cause the regulator to cut out as it goes into thermal shutdown.

If you have a way to get heat off of the regulator then 1.4W should be no big deal. That might be easier if you replaced it with a through hole part in a standard TO-220AB type case.

Another option, where you know the ballpark on your current draw you could wire a small power resistor in series with the 12V to drop the voltage before it hits the regulator to offload the bulk of power dissipation from the regulator. A 22 ohm 1W resistor at 0.2A would drop 4.4V and dissipate 0.88 W, leaving the regulator with only about 0.52W to deal with.

[sn96]

@EddieB

Another option, where you know the ballpark on your current draw you could wire a small power resistor in series with the 12V to drop the voltage before it hits the regulator to offload the bulk of power dissipation from the regulator. A 22 ohm 1W resistor at 0.2A would drop 4.4V and dissipate 0.88 W, leaving the regulator with only about 0.52W to deal with.

Thats a great idea. For now, if all you have is a 12v source, a cheap resistors is cheap insurance to protect the Bot board until you can get either a heat sink or a power source that is safe to use.