CoCo2 26-3134A with 230V~ ???

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jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

Thanks!

I will look at this after holiday :D

btw. i have seen that http://www.reichelt.de has also many tranformators...
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jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

OK... Start from the beginning, again...
sorchard wrote:As you say, the original transformer is effectively 2 x 8.6 VAC. Max current is 1.8A per output coil. Power rating is 17.2 x 1.8 = 31VA.
I search on reichelt.de again...

I would like to insert the transformator into the case, at the place of the origin transformator.
There is a place of 6,4cm x 6,8cm (better 6,4cm), heigh: 6,5cm

Best matches are:

"Universal transformer" in a "open design":
A.) 2x9V 24VA - 15€
-> http://www.reichelt.de/Universaltrafos/ ... T+24VA+2X9
* size: 6x5,5x5cm (fit the origin place)

B.) 2x9V 48VA - 20€
-> http://www.reichelt.de/Universaltrafos/ ... T+48VA+2X9
* size: 6,7x7,5x5,9 cm (to big)

"Toroidal transformer" as a "print design"
C.) 2x9V 25VA for 18€
-> http://www.reichelt.de/Ringkerntrafos/R ... RKPT+25209
* size: 6x6x3,8 cm (fit the origin place)

"Closed PCB transformer":
D.) 2x9V 36VA - 10€
-> http://www.reichelt.de/Printtrafos-25-5 ... 6%2F23+209
* size: 7,1x6,1x4,9 cm (too big, but can be easy fitable)
Image

E.) 2x9V 30VA - 10€
-> http://www.reichelt.de/Flachtrafos/UI-3 ... 9%2F21+209
* size: 6,8x5,7x3,5 cm (fit the origin place)
Image

Seems that D.) or E.) is the best choice, isn't it?
E is smaller but the "problem" is, it has two primary windings: 2x115V... IMHO i can use it with 230V by "series connection", isn't it?
D is a little bit bigger, but has only one primary windings for 230V and is a little bit more efficiency...

So D?

sorchard wrote:If your house doesn't have circuit breakers you should probably include an inline fuse on the 230V side. Something like T2A with >1000A breaking capacity.
Adding a fuse is a good idea!
The 25VA "Toroidal transformer" has a fuse with 230V 160mA...

Should i add a fuse on both sides? primary and secondary circuit ?
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sorchard
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Re: CoCo2 26-3134A with 230V~ ???

Post by sorchard »

Return of the jedie ;) I hope you had a good holiday.

Transformers D and E should both be OK. Transformer D looks a little better because the no load voltage is lower than transformer E.

I personally wouldn't use PCB mounting transformers in this way as the PCB mounting pins are not very strong. That said, if you make sure the wires can never pull on the pins then it shouldn't be a problem. You will need to improvise something to fix the transformer in place, perhaps stand it up on some posts if there is room.

If you wanted to use transformer E, then yes, the two primaries can be connected in series for 230VAC input. This is the main reason why many transformers have two primaries, so they can be wired in series for 230V, or in parallel for 115V. You just have to be careful to get the coils the correct way round otherwise you'll be shorting the mains supply. (There are usually phasing dots marked at one end of each coil: For a series connection, you need to connect a dot terminal to a non-dot terminal)

A fuse on the primary should give sufficient protection, but there's no reason why you shouldn't fit fuses on the secondary, except in the case it would break a connection to protective earth.

Inrush current into a transformer at switch on can be massive. (it could be 10x for EI transformers, 50x for toroids). I wouldn't expect a 160mA fuse to last very long. I would choose T1A minimum. Maybe T2A for a toroid.

I should say it's *very* important you see text like this on the transformer datasheet:

Sicherheitstransformator nach IEC 61558-2-6
Safety isolating transformer to IEC 61558-2-6

This is for protection against electric shock. You don't want the transformer insulation to fail when a 3000V spike appears on your mains supply...

I checked for you by the way: D & E are safety isolating types :-)
Stew
jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

Thanks for the response... Yes, holiday was good, but to short ;)

Then i will buy Transformer D. So i must not connect the 115V inputs ;)

Think i will fix the cables to the PCB mounting pins with hot glue and also fix the whole transformator with it ;)

Questions: I didn't have the origin "shielding covering cage" :( Should i try to do a handicrafts one?
(Have created a question on the CoCo ML, too.)
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sorchard
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Re: CoCo2 26-3134A with 230V~ ???

Post by sorchard »

jedie wrote:Think i will fix the cables to the PCB mounting pins with hot glue and also fix the whole transformator with it
You're scaring me now... You do of course mean that you will solder the wires on first, then protect the joints with hot glue ;-)
jedie wrote:Questions: I didn't have the origin "shielding covering cage" Should i try to do a handicrafts one?
The shield will be more for compliance with EMC regulations than for performance reasons so I don't recommend you try it as it would not be easy to make a good shield. IMHO having homemade metalwork near mains terminals is going to create a risk of electrocution, unless you fix the transformer and shield to the case securely with screws, ground the metalwork properly and ensure that nothing conductive can ever be closer than 4mm to a mains terminal.

It's a wonder I made it out of my childhood alive. I used to do all kinds of stuff like this without thinking about the safety of it :shock:
Stew
jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

"D.) 2x9V 36VA" is on the way... :D
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tormod
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Re: CoCo2 26-3134A with 230V~ ???

Post by tormod »

By the way, at the vintage festival, through the cool guys of steckschwein.de fame, I acquired a switched power supply which seems suitable for feeding a Dragon directly, also the form factor would be perfect for replacing the PSU board. One day I will try it out. http://www.pollin.de/shop/dt/Nzg5OTQ2OT ... 7188B.html
jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

tormod wrote:By the way, at the vintage festival, through the cool guys of steckschwein.de fame, I acquired a switched power supply which seems suitable for feeding a Dragon directly, also the form factor would be perfect for replacing the PSU board. One day I will try it out. http://www.pollin.de/shop/dt/Nzg5OTQ2OT ... 7188B.html
Interesting! I create a separate thread for this -> viewtopic.php?f=8&t=4967
... too many ideas and too little time ... Related stuff written in Python:
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jedie
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Re: CoCo2 26-3134A with 230V~ ???

Post by jedie »

I'm potter... and miss my hot glue gun :? ...insulating tape must be adequate...
jedie wrote:D.) 2x9V 36VA - 10€
-> http://www.reichelt.de/Printtrafos-25-5 ... 6%2F23+209
* size: 7,1x6,1x4,9 cm (too big, but can be easy fitable)
Image
Hm! With my multimeter I measure 11,4V~ idle voltage :(
Hope that's ok for the CoCo...

EDIT: Now it's connected. I measure 10,4V~ if ON and 10,6V~ if OFF between A3 and A1, see:
Image

Hope it is not too much, in the long run... :?:
... too many ideas and too little time ... Related stuff written in Python:
Dragon 32 emulator / PyDC - Python Dragon 32 converter: https://github.com/jedie/DragonPy
DWLOAD server / Dragon-Lib and other stuff: https://github.com/6809
sorchard
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Re: CoCo2 26-3134A with 230V~ ???

Post by sorchard »

jedie wrote:Now it's connected. I measure 10,4V~ if ON and 10,6V~ if OFF between A3 and A1
It does look a little high. The transformer data sheet says the open circuit voltage should be 9 x 1.11 = 10V

If Q1 heatsink doesn't get too hot then it shouldn't be a problem.

Do you have another multimeter you can try?
Stew
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