Saturday, February 16, 2008

iRobot Roomba Charger for 220/240V Supply

You may be intending to buy (or have already bought) an iRobot from US for use in countries (like Europe, Australia/NZ or South East Asia) where the electrical outlet provides 220Volts or 240Volts. Using the given US charger on this outlets will definitely kill it instantly.

We all know why we would want to buy directly from US instead of getting it locally. Probably the model that we want are not available locally. But even if it's available, it may cost a bomb more than importing it yourself. But how can we actually use the imported iRobot on our local electrical supplies?

WARNINGS and Disclaimer

Before we begin please read the warnings and disclaimer!

1) Bringing the Roomba or Scooba for use out of USA/Canada voids the warranty.
2) The iRobot manual explicitly prohibits using of any power converter. Ignoring this warning voids your warranty.
3) Using any charger other than the provided original voids your warranty.
4) Any modification of the Roomba charger will also void your warranty.
5) As warned on the back of your charger, there is risk of electric shock if you open the charger. This electric shock can be fatal.
6) You should carry on the charger modification only if you are experienced in electronics. Otherwise, do not even try to open the charger casing!
7) Any mistake in the modification can lead to components EXPLODING & causing FIRE.
8) Electrolytic capacitors have polarity and will blow if placed wrongly.
9) If you insist to take the risk of modifying your charger, you will also be taking the responsibility for any problems that could arise.
10) The information provided below are for educational purposes only. Should you proceed with any of the options, we are not responsible for any damage arising from the use of this information.

So what are my options?

Basically, there are a few options, but please read the disclaimer before proceeding...

1) Buy an original charger for use on the 220V supply

I'm not sure how much your local dealer would charge for one of these, or whether they might even sell you one. But this would definitely be the safest option.

2) Use a transformer

A transformer, also called Power Converter or AC/AC Converter, changes the voltage of the supplies. Step-up transformers change a lower input voltage to a higher one, and a step-down transformer does the opposite. There are others which is able to do both step-up or step-down. What we are concerned here is the step-down transformer, changing the input voltage from 220V to 110V.

How to use the transformer? It's simple. Just plug it to your wall socket then plug the original iRobot charger to this transformer and you are done. :)

For the 500 series Roomba charger, it requires an input power of 33W. So we'd need to get a transformer that is rated minimum 35W.

However, it has been reported that a 35W transformer does not give enough power to fully charge the roomba, and the recommended rating is 70W to 100W. Be sure to get one that is industrial grade, otherwise your transformer would easily overheat and turn itself into a piece of junk. Mine did! :(

3) Use a universal power supply (UPS)

A universal power supply allows you to adjust the output voltage that you require. It usually has different sizes of output jack for you to plug into the various appliances. Some people use an adjustable laptop power supply. This is fine, because you'll just need the correct voltage and current to make it work.

For this option, simply replace the roomba charger (yes, you can keep it back into the box) with the universal power supply, shown on the right. So the UPS would connect to the home base. Since this is a replacement of the iRobot charger, the output voltage to the home base or roomba needs to be correct.

Let's look at our the charger specifications for Roomba 500 series. It says that the output voltage is 22.5VDC, and output current is 1.25A. So you'll need to do is to adjust the voltage on your UPS to about 22V and voila!

On some UPS, the output voltage is fixed. All you need to do in this case is to ensure that what you buy supplies a voltage of 22VDC and current of around 1.25A. There are cases of people using 22VCD with 1.6A current and there's no complains so far.

4) Mod your charger

This is the most dangerous of the few options available. Please read the disclaimer before proceeding. If you do not have any technical experience in electronics, please DO NOT try this option. A single mistake could cause your charger to blow into ashes. However, if you insist to take the risks and responsibility, continue reading...

The following describes how to mod the white Roomba 500 series charger (model 17062). Before beginning, remember to remove the charger from any power source, and ensure that the LED light on the charger is not lit.

What electronic components are needed for the mod?

We only need two electronic components for the mod.
1) 47uF 400V capacitor
2) Varistor rated between 270 to 380 volts (optional)

What to do?

First, to open up your charger you'll need to remove the white rubber studs under the charger. Removing them will reveal the screws.

After opening up the charger you'll see the charger circuitry. We are mainly concerned with 2 components in this mod. These are the C1 capacitor and the RV1 varistor.

We'll need to replace the capacitor C1. The original C1 capacitor (CapXon 47uF 200V) is rated at 200V and would blow if connected to the 220VAC socket.

Therefore, we'll need a capacitor that can cater to the 220V or even the 240V supplies. To find out the rating we really need, we use the following formula:

(AC RMS Voltage) x (sq root of 2) = 240 VAC x 1.414 = 339.4 V

Why do we need to multiply by square root of 2? If you study electrical and electronics, you'll know the reason. :)

So, having calculated the peak voltage of the AC current supply, we can find the right capacitor to use. We choose the 47uF 400V capacitor to give some extra voltage allowance in case there is a slight surge in the peak voltage.

Please remember to place the polarity of the capacitor correctly. Failure to do so might blow up your charger!

Usually we'll be getting the bigger version of the 400V capacitor, so before soldering, we need to ensure that there's enough room to place the capacitor. On the left, you can see a picture of how mine is placed. It's not advisable to leave the leads unprotected. I won't want them to touch each other and cause a short circuit, so I used a PVC tape to insulate each of the capacitor leads.

Once you are done with replacing C1, you can move on to the next step.

We need to replace or remove the blue RV1 varistor. The varistor is to protect the unit from power spikes. What it does is to conduct significantly increased current when the voltage becomes excessive.

The provided varistor is 10D271K. This is rated for a maximum VAC of 175V which is lower than our 220V or 240V supply. We will need one that is rated at least 270V in order to work on a 240V supplies.

If you cannot find a suitable varistor locally, you will just need to remove the varistor. It will still work this way, although there'll be one less level of protection for your charger.

Lastly, you'll need to change the power plug from the US 2-pin plug to your local 2 or 3-pin plug. Alternatively, you can get an adaptor for this, though the former method may be more convenient in the long run.

To summarise...
1) Proceed with the modification only if you have experience in electronics.
2) Replace C1 with 47uF 400V capacitor. Be careful of the polarity of the capacitor when doing this, any mistake can cause an explosion or fire.
3) Replace RV1 with a 270V and above varistor. Or simply remove it.

Testing the modded charger

Before you really plug the charger into the homebase or roomba, you should test the mod. Afterall, it's cheaper to get a new charger than to replace the entire roomba if anything goes wrong.

Screw back the charger casing, so that if anything blows (touch wood!), it's contained within the casing (hopefully...). Plug the charger to the power outlet and use a digital multimeter (DMM) to measure the voltage. It should read around 22.5VDC. If you try to read the current, the LED should blink and the readings would jump. This is normal.

Once everything is done, you are good to go!


Note: iRobot, Roomba and Scooba are the property of the respective trademark holders. None of the trademark holders listed here are affiliated with us.