Using a 3.3v Microdrive as a CF hard drive

[Allen1]

Recently I bought some 6GB second user microdrives to play with. An Amiga would happily work with a similar 4GB drive like this if it was a 5 volt version, realistically the power in an amiga and most computer devices is reasonably stable (unless the is a real problem of course).

Using diodes to drop the voltage from 5 to 3.3 (using 1n4001's) should have probably needed 3 but I found that there was insufficient voltage to power the drive, using just 2 seems to have done the trick, this however is using a PC's USB 2 1/2 external drive interface. An alternative would be to use a voltage regulator from the 12v line and power the CF card from that.

Has anyone got a simple idea to use a 3.3volt drive in an Amiga 1200 or 600 other than the diodes or something better than just the diodes in series as I used.

Steve Fitzgerald pointed out an auction for 4GB drives which are 3.3v hence this post

The card looks dirty but its the remnant of some sticky sided foam I had on it + the fact I still can't take a decent picture

Oh yes the track to cut is on the legs next to the last one and use a wire from the end of the diodes to connect to the other side of the track that was cut (I soldered the diode to the legs)

::::::::::::::::::::|:

Those legs | are the 5v power in looking from the back of the card as in the pictures.

[fitzsteve]

Nice work Allan =)

Whats with the 'Steve Fitzgerald' though

I consider us friends, you can call me Steve

Any chance, being useless at these things myself; I could send you my spare CF adapter for modding? Since I bought one of those drives before knowing the voltage...

I will include a little gift for you and some stamps for the return leg

Steve.

[Allen1]

Originally Posted by fitzsteve

Nice work Allan =)

Whats with the 'Steve Fitzgerald' though

I consider us friends, you can call me Steve

Any chance, being useless at these things myself; I could send you my spare CF adapter for modding? Since I bought one of those drives before knowing the voltage...

I will include a little gift for you and some stamps for the return leg

Steve.

I was on a different area of the site when I wrote that and couldn't for the life of me remember how to spell "fitzsteve"

Sure just send your card, I'll post it back as it will only be a few pennies anyway and I would use the same envelope etc. Hopefully by then someone will have made or posted a better idea though

[fitzsteve]

Its ok, aparantly I can't spell Allen

Thanks for this by the way, you are a true gent

[Allen1]

Originally Posted by fitzsteve

Its ok, aparantly I can't spell Allen

Thanks for this by the way, you are a true gent

I have been called worse than Allan and sometimes I am OK-ish but not as often as I ought to be and sometime a bit more argumentative than I should be but hey that's what makes us all different isn't it

You are a really good bloke too

[musashi5150]

Get a room

[Allen1]

Originally Posted by musashi5150

Get a room

Oooh you are awfull................. but I like you Nice one M8

[Hewitson]

3.3v zener diode would be a bit better.. At least you'd have some form of regulation then.

[Allen1]

Originally Posted by Hewitson

3.3v zener diode would be a bit better.. At least you'd have some form of regulation then.

Hi there Hewitson,

in the past I used fixed voltage regulators like the LM7805 or adjustable ones like the LM317T in many projects but never really used a Zener if I recall correctly. Anyhow I took onboard your suggestion to prevent over-voltage problems and added a 1/8th Watt resistor and a 3.3v Zener, the Zener is a BZX79C 3.3v 1/2 Watt one and the resistor is there to act as a current limiter and is of a low value (13 ohms) to allow the zener to work, NO mathematics have been used to come up with that value, its what I have on hand and the actual voltage that will be supplied will vary from Amiga to Amiga.

So basically the 5v supplied to the CF card adapter has had the track cut and is now diverted through 2 1N4001 diodes which then feed the power to the board, at this point the resistor and Zener diode are connected and any over-voltage is sent to GND, it does seem to work as the resistor does get warm which would indicate that power is being diverted through it.

@fitzsteve

The 4GB microdrive's cause the hard drive LED to stay on, using a CF card things work fine the same for those 6GB microdrive's I got, so these ones are designed for cheapness rather than compatibility but hey at that price you can't go wrong

On the 3rd picture you can see where to cut the track, you will then need to scrape off the lacquer as in where the copper is exposed, this is for the diodes to solder to (the 3.3v in)..

[fitzsteve]

Originally Posted by Allen1

@fitzsteve

The 4GB microdrive's cause the hard drive LED to stay on, using a CF card things work fine the same for those 6GB microdrive's I got, so these ones are designed for cheapness rather than compatibility but hey at that price you can't go wrong

On the 3rd picture you can see where to cut the track, you will then need to scrape off the lacquer as in where the copper is exposed, this is for the diodes to solder to (the 3.3v in)..

Thanks for the info Allen, the HDD LED staying on would really peev me off so I guess I'll just use mine for storgage.

I'm glad you pointed it out before I fried something though lol

Steve.

[Allen1]

Originally Posted by fitzsteve

Thanks for the info Allen, the HDD LED staying on would really peev me off so I guess I'll just use mine for storgage.

I'm glad you pointed it out before I fried something though lol

Steve.

The simplest way to stop the Hard drive LED from staying on with these cards is to not fix the onboard LED ie the wire on the right of the board to the LED, it would just mean there would be no LED flashing when the drive is being accessed.

[fitzsteve]

Originally Posted by Allen1

The simplest way to stop the Hard drive LED from staying on with these cards is to not fix the onboard LED ie the wire on the right of the board to the LED, it would just mean there would be no LED flashing when the drive is being accessed.

I thought so but that peeves me off too

Yeah I know I'm a bit

[Hewitson]

Good to hear my suggestion worked for you. Personally I would have gone for a zener with a higher power rating and done away with the 1N4001's.

[Allen1]

Originally Posted by Hewitson

Good to hear my suggestion worked for you. Personally I would have gone for a zener with a higher power rating and done away with the 1N4001's.

Hi there Hewitson,

Using that method would involve a 4 or 5 ohm 1 to 2 watt resistor and a 3.3v 1.5 to 2watt zener depending on actual maximum current required by the drive, onboard LED and the actual zener. A Hitachi 4GB drive has a rating of 16 mA on standby and 305 mA when writing. I didn't measure these drives though as I hadn't intended on being current dependant for the power source. Taking into consideration the extra heat that this method is likely to generate, I think the overflow method I used would probably be more effective and less power consuming in this case but as I previously mentioned, I have not had anything to do with zeners in anything I have previously built.


http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

[Hewitson]

Originally Posted by Allen1

Taking into consideration the extra heat that this method is likely to generate, I think the overflow method I used would probably be more effective and less power consuming in this case

Oh yeah, without a doubt.

However the fewer components there is, the less there is to go wrong

[orange]

my CF adapters have a jumper for 3,3 or 5V power. why don't you just get one like that?

[Allen1]

Originally Posted by orange

my CF adapters have a jumper for 3,3 or 5V power. why don't you just get one like that?

Now that is a handy card, I didn't realise you could get those. That would have been very useful for the 2GB Kingston elite pro 50x CF card I had which stopped working, I then found out that it was a 3.3v only version (I should have read the label on the back)

The ones I just found are:- this and this

I see that those cards use either 2 or 4 SS12 20 volt, 1 amp Schottky surface mount diodes (2 on each side of the board on the ones I just found), these diodes drops 1/2 a volt from input voltage to output ie 5v in 4 1/2 volts out, so using two would drop 5v down to 4v and using four would drop 5v down to 3 volts. I don't have one of those boards, so how many of the diodes are being used is unknown to me at the moment.

The diodes I used were 1N4001's and the voltage drop is .7v each, so through 2 of those is typically 1.4v which from a 5v supply would give 3.6volts, most of our Amiga power supplies seem to give less than the full 5volts going off mine and several posts here, and with the added zener, any over-voltage is drained away. A bit of the belt and braces approach maybe.