Electronics > Beginners
28vac transforer to 24vac possible?
bob91343:
All good comments. The distillation is:
1. Get the correct transformer.
2. Use a dropping resistor.
3. Take a chance and use excessive voltage.
4. Modify the new transformer.
Any of these three will work with varying degrees of success.
shanezampire:
Well my project got complicated. I had an OK Industries SA-1001 missing the handle and they are hard to find and cost a ton. It was "female" 6 pin. I ordered a 6 pin Hakko 8001 6 pin handle which is a male plug. The pin lay out is totally backwards and nothing like like the Hakko. Ground is like pin one or two on the OKI, heater like 3 and 6 .. just odd and weird than standard. I jumper-ed them correctly and the transformer/iron works fine. The board of the OKI is either fried or don't work right. It will not control the temperature. Its full power/temp.
I said heck with it and ordered a T12 control board, handle, buck converters, and all I need to hook the T12 to the 28v transformer.
Now I have decided to just buy a large project box, a 24v 4.5 amp power supply for the T12 kit, which is a "male" 5 plug. That will cover the T12 handles.
Buy a 936 control board which uses a 5 or 6 pin "female" plug and will accept various handles. I have checked the lay out of various pin outs and resistance on heaters/sensors on Hakko style handles.
So in the end I will solve my problem by having a box with a plug and control board to control which ever handle I find cheap or have (Hakko style that is)
Messing with this OKI station... now I already have a collection of several style Hakko handles, extra tips, with female/male plugs goofing off with this OKI station.
So I already have this good 28v transformer. I hate to just buy another one and spend more $ on a new 24v one > https://imgur.com/a/ixcBOFu
If they are a simple and cheap way to make it work with that 936 board I ordered.
The 936 board I bought is this one - https://www.ebay.com/itm/A1321-For-HAKKO-936-Soldering-Iron-Control-Board-Controller-Station-Thermostat/112719961476
I already have spent a lot of $ trying to make this OKI work but I have learnt (especially reading here at EEV and messing around) a lot so in the end it is all worth it.
mariush: I got the voltage off the transformer 14/28 unloaded it measures 16 / 33 volts VAC about 20-ish one side VDC through a bridge rectifier and smoothing capacitor unloaded
shanezampire:
So from what I gather is a resistor will be the simplest.
The transformer is a - A41-80-28A33 is made by Pulse 28VCT 2.8A or 14VAC 5.6A 80VA
The board above says I need - AC adapter 24V 3A transformer OR HAKKO 936 Iron Fist compatible A1321 Central heating Characteristics
Online calculators says if I use a 1.42 Ohm resister for 2.8 amp draw or 1.33 Ohm resister for 3 amp draw that will reduce the voltage to 24v - Minimum Resistor Wattage 12
So If I order a 1.5 Ohm 25 - 100 watt resistor I should be just where I need to be .. Correct?
shanezampire:
Scratch the above. I just found a 1.5 Ohm resister and tried that. Unloaded voltage from transformer was 33v. I hooked a Hakko FX-8001 handle to it (straight to the heating element) and the voltage dropped to 30v. I then attached the 1.5 Ohm resister and the voltage only dropped to 27v
bob91343:
So the current draw is less than you thought. You can play with the resistor value until it's where you want it but it really isn't critical, other than possible overvoltage to the control board.
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