Milliamps and voltage help please

I have just bought a remote wireless camera from china and straight out of the box and setup is stunning.. I use a tiny first person view Sony camera and it gobsmacking quality. I took the camera down to the end of the garage and plugged it in via the wall sock power, according to destructions it uses 7 – 12 v and 400 mAh’s and I went back in the house upstairs at the far end to my bedroom and the quality again was stunning. So that’s about, in a straight line 80 feet through some pretty thick stone cottage walls and concrete block garage. But now I have a problem, which is why I need some advice. I ran the camera on a 9v NiMH 9 v 150 mA battery , went back to check and I didn’t expect to see anything but there was a pretty good quality picture, it did get a bit snowy now then I disappeared when I went near the receiver antenna. That’s fair enough I wasn’t expecting anything less from 150 mAh’s.
But I have a 7.2 v “1200” mAh battery, used for RC cars. So the question is can I use 1200 mAh’s on a 400 mAh piece of equipment or should I somehow reduce the output. Would it burn the camera or transmitter out or would it increase its range? The tank I’m putting it on works on 7.2 v’s and I have a 3400 mAh battery for it, what I would like to do is somehow build a power distribution board but don’t have a clue where to start.

No expert here but to me the Ma rating will be what it draws when working at max so giving it higher doesn't mean it will draw more just that more is available if needed and will run for longer if the battery is the sole power source.? IE: 3400ma/400ma=8.5hrs use

Fivetide; JAZZCNC is dead right here. It matters not a jot what the battery capacity is; it's all about being of the appropriate voltage and of sufficient capacity. Even if you could get and use a battery with 1000000 Ah capacity it'll be fine, so long as V is OK. Mind you the battery would be huge but last for ages!

Just remember I=V/R Ohm's law.

Thanks chaps .. great answer :)

Only downside to running the camera straight off the tanks battery is that the tank won't run for quite as long on a fully charged battery but the camera will be drawing next to nothing so won't make a great deal of difference.

Hmmm

If it wants 7-12V then you can run a 9V battery a lot flatter than a 7.2V battery before it drops below 7V. The poor things do tend to fade before they reach their rated Ah.

I think it's looking for a 9 Volter.

Is it really drawing 400mA?

0.4A at 9V is 3.6W. Sees like a lot, does it run hot?

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Originally Posted by Robin Hewitt

Hmmm

If it wants 7-12V then you can run a 9V battery a lot flatter than a 7.2V battery before it drops below 7V. The poor things do tend to fade before they reach their rated Ah.

I think it's looking for a 9 Volter.

Is it really drawing 400mA?

0.4A at 9V is 3.6W. Sees like a lot, does it run hot?

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Actually after looking again , its running at 260mA / 800mW, I think also the voltage may affect the range, as it quotes 800m to 1600m @ 12v/280mA's So I might be better finding a 12v battery if I want the better range. The more powerful ones quote 900mA's/2500mW's

Wireless AV

I hope the tank battery is NiMh/NiCd not LiPo? If it's the latter then you need to be careful as they require a low voltage cutoff to stop them being damaged from over discharge. If it will tolerate up to 12.6V then a 11.1v (3 cells in series) lithium battery would be ideal since when fully discharged it would still be around 10V. Plenty on HobbyKing RC Plane, Car, Heli, Boat and MultiRotor Hobby Store ... if it's the first time you've seen that site you'll no doubt be up all night buying better batteries and all sorts for the tank!

What sort of size is the tank it's going into? Sorry don't know much about radio controlled models except some seem to be quite big. Just thinking that a 12v battery from one of those motorized cycles would probably do a good job. Friend of mine lent me 2 to power a small trolley & I was surprised how powerful they were for such a compact size battery.

Problem with a 12 Volt battery is you will get over voltage when fully charged. 9 Volts really is the best bet, unless you pop in a regulator.

Can you get a 9 Volt regulator or do they leap from 6 to 12? 12 would very quickly have the same problem, even if low drop out.

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Originally Posted by Robin Hewitt

Problem with a 12 Volt battery is you will get over voltage when fully charged. 9 Volts really is the best bet, unless you pop in a regulator.

Can you get a 9 Volt regulator or do they leap from 6 to 12? 12 would very quickly have the same problem, even if low drop out.

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Yep, LM2940CT-9 Buy Low Dropout Voltage Regulators 1A,9V,LDO Voltage Regulator,LM2940CT-9.0 National Semiconductor LM2940CT-9.0/NOPB online from RS for next day delivery. 9v out @ 1A max, max 0.2v dropout @ 100mA, typ 0.5v @ 1A. Only £1.33 each. They do a 10v one as well.

As an alternative MC2941 http://www.rapidonline.com/Electroni...egulator-65305 @ £1.75 will also do the same, but is programmable for any output voltage with 2 resistors.

Either will handle 12v -> 9v @ 400mA with no heatsink (tho case will be > 90degC so hot!) but a small clip on heatsink would be advisable (or just a couple of sq in of ally) if using a lead acid cell or other battery thats at 13.6v fully charged

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Originally Posted by martin54

What sort of size is the tank it's going into? Sorry don't know much about radio controlled models except some seem to be quite big. Just thinking that a 12v battery from one of those motorized cycles would probably do a good job. Friend of mine lent me 2 to power a small trolley & I was surprised how powerful they were for such a compact size battery.

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Maybe if people are interested I should start a new thread I explain what I'm trying to do and get help with trying to it ? May help others in the future.

He's going to attack the Reds from his living room via the Interweb.

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Originally Posted by boldford

He's going to attack the Reds from his living room via the Interweb.

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I have T59 I know the weakspots lol Thread started if anyone is interested, I'll post as I go :)