Power Adapter that will replace 3 AA batteries

[keeney123]

I have a Petlinks toy that has 3 AA batteries it runs on. I have tries to use a Panasonic EB-CA340 AC adapter to replace the batteries which has failed. The supply is 5.6 Volts at 400 ma. I have tried the supply by itself. It lights the on light of the pet toy, but then goes out. I tried a various voltage divider circuits 4.6 volts and 5.3 volts. I have used both high resistance voltage dividers and low resistance dividers with the same result. I even used a computer power supply at 5.3 volts. The computer supply did not even light the on light. All the time I used these supplies I monitor the voltage with a multimeter and the voltage stayed the same as the open circuit voltage. I even tried to put a micro and milli amp meter in series with the three AA batteries but the toy would not turn on. I wonder if someone out there knows of a adapter the will emulate the characteristic of three AA batteries in series? I do not want to have to built a linear adapter I was hoping that their already is one on the market. I have been unable to find one on the internet nor are the full specifications supplied with one one's on the internet.

[budm]

Re: Power Adapter that will replace 3 AA batteries

May be they also tap part of the batteries connection to get lower Voltage beside the 4.5V of the total output. You need to look at the batteries holder to see if it has two wires from the batt holder.
"Panasonic EB-CA340" is this linear power supply wallwart or regulated output? If it is non regulated linear then the out put will be much higher (around 8V) than 5.6V without full load of 400mA which could have damaged the circuit..

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

It only has two wires. One going to the neg.terminal and one from going to the positive terminal. The three AA batteries are in series. The only information I have is that the adapter is made by I.T.E. for a Panasonic Cell Phone. I.T.E says all their adapters are regulated and that seems right because I did not see a change in voltage. Linear is a funny word. The places that sell power supplies or wallwarts use linear to represent non-switching supplies. My understanding is all wallwarts from about 2002 are switching. Also, the circuit is not damaged as when I replace the batteries it works fine. The internal resistance of a AA battery is about 0.2 ohms at room temperature. The only thing I can think off is this engineer is going a ERS measurement before he starts the program.

[budm]

Re: Power Adapter that will replace 3 AA batteries

Did you check the current draw, especially at start up when it works with AAA?
There are still lots of Linear (unregulated and regulated) power supply out there. the Linear lasts much longer than the SMPS type but it uses more power and not green due to power consumption in standby mode, vampire power.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

Yea, I tried to check the current draw but the device would not operate with the meter inline. I figure if I put the linear adapter under a switch receptacle and only use it when the cat wanted to play it would not be quite a Vampire. I can not find any spec online that would tell me if these supplies are not switching. Do you know where I might get a non switching adapter that is 4.5 volts without having to make one?

[stj]

Re: Power Adapter that will replace 3 AA batteries

4.5v - rings a bell, a door bell.
go look for a bell transformer.

or get a variable supply, you can get wall bricks with a switch: 3v, 4.5v, 6v, 9v, 12v

[budm]

Re: Power Adapter that will replace 3 AA batteries

"Yea, I tried to check the current draw but the device would not operate with the meter inline." More likely that the fuse for the over current protection in your meter is blown.

[SteveNielsen]

Re: Power Adapter that will replace 3 AA batteries

"I even tried to put a micro and milli amp meter in series with the three AA batteries but the toy would not turn on."

Use the 10A DC range, the current you tried to measure is too high for the milliamp range.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

We are talking about 3 AA batteries if the current was around 10 Amps the toy would not run over 12 minutes. These batteries life expectancy are rated somewhere around 2200 mah. That is 2.2 amps in one hour.

[budm]

Re: Power Adapter that will replace 3 AA batteries

If the fuse for the current protection is blown, it will explain why the toy does not work when you put the meter in series with batteries.
My Fluke 87 has two fuses for current ranges, one is only 400mA, another one is 10A.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

Yea, your right it is blown. I thought the milliamp rating of my meter went to 1.0 Amp but it only goes to, they say 400 ma, but it is fused for 500ma. This must be the start up current because I can't see operating at 500ma. It would only last 4.5 hours. It still does not explain why the computer supply did not operate the toy. The other adapter had a current rating for 400 ma. So I can see why that one did not work. I will now connect the Amp meter back using the 10 A setting. Thank Guys.

[budm]

Re: Power Adapter that will replace 3 AA batteries

If it has dc motor, the inrush current can be easily be 10 times the running current (Applied Voltage divided by Armature resistance = Ia).
http://www.electrical4u.com/starting...e-of-dc-motor/
You meter has to be fast enough to catch the inrush, my Fluke has Peak hold reading and can capture 1mSec Pulse.
So we know it draws more than 0.5A for sure since the fuse blown.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

I was able to measure the running current. When on first turns on it is on slowest speed. That I=0.460 A so the resistance is 9.82 ohms because the running voltage is 4.56 volts down from 4.60 Open circuit voltage. Which is about 0.046 ohms internal resistance of the batteries. They are lithium 1.5 volt. The ATX supply still will not drive this using the 5 Volts that measured 5.3 volts. It says its I rating is 32 Amps at that voltage. That is the only thing the supply is driving. So, maybe a linear Adapter that has 5 Amps of current, if inrush is 10 times the amount?
Sounds more like a power supply than an adapter.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

I believe the motor is a stepper motor because it is able to turn directions at the drop of a hat, so it must be getting pulsed. Is far as the a hold setting on this meter I do not see any DC current freq specification,only AC current frequency specs. and the DC pulse width is measured in voltage +5V to 0V. Some of this stuff is coming back to me communicating with you guys. It has been 20 years since I did circuit analysis and 35 years since I graduated College.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

BudM I was just able to click on your link. Seems like an awesome sight for teaching. This will refreshing my memory. Thank you.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

BudM I was able to find a power supply schematic for a stepper motor from the site you so kindly shared. It will take me a while to get all the parts and look up the specs so I can supply the 5 volts. I have to get the right transformer, bridge diodes etc. It looks like using a TIP 2955 to sink the in rush current will work.

[keeney123]

Re: Power Adapter that will replace 3 AA batteries

I decided not to build the supply because the cat got bored with the toy and only likes me moving the feather on a stick so it would be wasted to make a power supply, but thanks guys for your support.