Hey Ron.

So what sort of gizmos will a typical "Head" you would be using have (servos, sensors, camera ect), just so we can get an idea of what power requirements they will need?

It always comes down to the amps, not the volts. The EZ-B will actually run on 5v, you just need to disable the low battery warning. But 1/2 amp is barely enough to keep the EZ-B itself running. Certainly won't be able to use the camera or LED array. Can probably use the speaker.

Alan

Good questions Steve and Alan,

For prototype head, I see just the gizmos that come with the JD head. At this time, I don't have an inkling what head or heads will be used in production, and what amp needs they will have. So for now, I guess I should be able to answer the question for the vanilla JD.

Ron

So does the 2 LiPo battery pack provide 7.5 V at 500mA? Should that be the target of a direct connect?

Ron

Actually the 7.4v LiPo battery pack sold in the store could potentially provide about 30 amps, but that would only be for a few minutes. As Alan has mentioned, is really not a lot of power at all. Most sensors need very little amperage, a camera will need a little more as with LED arrays, and sevos will need the most amperage to deal with the initial in-rush current to make them move.

To run an EZ-B with a JD head with the included LED array and camera (not forgetting the head comes with two micro servos), you should get a good couple of hous run time with a 7.4v 1300mah battery. Or you could use a power adapter which can knock out a few amps, and should run the v4, camera and LED array okay (if you intend to use servos as well, you will need to look at double figures for amps, around 15 to 20 depending on how many servos you would use).

Yeah, Steve, the neck servos will be important.

Wouldn't the best bet be to try to reproduce the "power" provided by the typical LiPo battery pack? That profile would be able to handle most anything a prototype would need.

Ron

Yeah, if you can reproduce the power (voltage and amp output) that a LiPo or Nimh battery can offer, than that will be fine.

To handle the servo inrush current you'll need at leasr a 10 amp supply at 7.5 volts. 20 would be better but with just the 2 head servos 10 should do. Most of the time the draw will be much less, but whenever the servos start to move they pull a lot of amps for a very short time (inrush). Search the forum for inrush current or in-rush current and there are dozens of posts about EZ-B 's resetting and every one of them was using an insufficient plug in power supply or alkaline batteries.

Alan

@Alan

Ok, so a 20 amp supply is a good target. Just looking around a little, I found this:

P/N: RSP-150-7.5 7.5vdc Power Supply Approx Power: 150 Watts Max Current: 20 Amps Enclosed 1U low profile 30mm, built-in active PFC function, built in constant current limiting, LED indicator for power on, adjustable output voltage, and universal AC input range: 85~264vac. Dimensions: 199x99x30mm More Info, Quotes, Purchase $36.90 ea.

This quick result gives me a pricing basis for my business plan.

Thanks to both Steve and Alan.

@MathProf,

Here are 2 "wall wort" power supplies that you might want to consider from Jameco:

AC to DC Power Supply Wall Adapter Transformer Single Output 7.5 Volt 1.73 Amp 13 Watt ~13.95 http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2101817_-1

AC to DC Power Supply Wall Adapter Transformer Single Output 7.5 Volt 2 Amp 15 Watt ~12.95 http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2102748_-1

A 5VDC, 20Amp supply can be used. The camera and LED eyes will still operate just fine as they are powered by the regulated to 3.3V. But as mentioned the low battery warning setting will need to be adjusted to use 5V.

4.5V is the minimum voltage input before the regulated 3.3V is affected.

Edit: The ez-b plus camera only draws ~180mA peak but servos can draw crazy amounts of peak current.

Just remember. Any voltage can be stepped down, so a power supply with higher voltage than needed can be used. Just get converters that handle high amperage.

I have had a hard time trying to find wall adapters that supply 2amps! So your quest might lead you to a bench test power supply, or a PC power supply. With a PC power supply, check what each voltage line can output. The 5v line could do one amperage while the 12v does another.

OldBotBuilder, Jeremie, and Technopro,

Thanks for the info and suggestions. So, Jeremie, looks like 5V/20A might be the best route for my experimenting. However, if as Technopro says it's not easy to find such a wall adapter, maybe the most straightforward approach is to look at a PC power supply - I can see how the two supply voltages could handle multiple amp requirements. I'd need to compare cost of a PC power supply with the approximate $37 cost of the converter I found and posted in #10 above.

Thanks again for your help!

Ron

I think the $37 one you found is probably a good bet. If you were to buy a battery and charger for each location, you would be talking about $45 per location, with less convenience. 20amp at 7.5 volt is sufficient to drive a whole JD, not just the head (and probably enough for something like an Alan or InMoov head too).

Alan

Cool, Alan. Saving $8 per unit is good news.

Ron

Do you have a link for that power supply? I might want to test one.

Alan

Alan,

http://www.trcelectronics.com/7.5-volt-power-supplies-chassis-1.shtml

Ron

thanks

Alan

Please specify the power consumed by your one head means the total power consumed by the all components consisted in one head. According to that calculation you can select that which power supply will be suitable for you. But it is looking that the power through USB will not be enough you must think about the direct power from the wall outlet.