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Electronics => Projects, Designs, and Technical Stuff => Topic started by: raptor1956 on January 03, 2018, 04:25:16 am

Title: TO-220 pin clips
Post by: raptor1956 on January 03, 2018, 04:25:16 am
I'm bread-boarding a project using Peltier modules and a heating element and am using two P-channel MOSFETS as the power switches.  I have the devices plugged into one of my bread-boards where you push the pins in but I noted a while back that I managed to burn a board using, maybe, 4A so I decided to not run the higher currents through the bread-board and instead clip directly to the MOSFETS pins while allowing the connections in the bread-board to handle the control signals from NPN transistors.  That is, each circuit has an NPN transistor that receives it's control signal from a Teensy 3.6, limited to 3.3V, and then the NPN drives the MOSFET gate at full voltage (10-15VDC).  The NPN's are acting as voltage isolation and gate drivers.  The heater circuit is easier as it's limited to about 2A but having burned up one nice proto board I'm gun shy about over driving the buss in them.

Anyway, since the MOSFETS are plugged into the bread-board to facilitate the control signals from the NPN, but I chose to bypass the bread-board for the higher currents which, in the case of the Peltier, is about 4A.  At present I'm using some mini-gripper type clips but they are a bit bulky and barely fit.  Is there a better solution for connecting higher current conductors to the TO-220 pins while the package is plugged into the bread-board?  I could remove the MOSFETS from the bread-board but then I'd need to run additional wires from the bread-board to drive them and the project is already pretty rats-nesty with wires.

Title: Re: TO-220 pin clips
Post by: Ian.M on January 03, 2018, 05:09:28 am
Nope.   I've never seen a clip that would make multiple reliable contacts to TO-220 pins and still leave enough of the original pins exposed to plug into a breadboard.

Any time you put more than a few hundred mA through solderless breadboard contacts, you are asking for trouble, so the intelligent thing to do is to move the power circuits off the breadboard and solder their connections.   If you solder the MOSFETs to strip or matrix board to make a daughterboard,you can use a right angle 0.1" pitch header on one edge to let you plug it directly into the breadboard, and also put ordinary headers or even screw terminals on the daughterboard to connect the power wiring.   

For larger power circuits, or anything that needs a heatsink, its a bad idea to plug the board directly into the breadboard, just due to mechanical issues.  If its got lots of interconnects to the breadboard, a ribbon cable with an IDC DIL header on the end is convenient to keep the interconnects organised, otherwise simply use individual jumpers with Dupont pin ends.  It will be more reliable if your power module is mounted to the same base as the breadboard so there is no relative movement when handling it.

One occasion where it is useful to add an extra wire to a TO-220 pin in a breadboard is when using LM78xx or LM79xx regulators, as if the common pin comes loose they will loose regulation and pass a volt or two less than their input voltage to their output, probably blowing its load.  Soldering an extra wire to the Gnd pin as close as possible to the body allows you to use separate strips for Gnd in and Gnd out so if there is a bad connection the worst that happens is its load looses power. 
Title: Re: TO-220 pin clips
Post by: xani on January 03, 2018, 05:41:20 am
I'd just get a small protoboard and make a breakout with separate power in, power out and control in (with a bit of extra wire for power path).
Title: Re: TO-220 pin clips
Post by: helius on January 03, 2018, 06:07:41 am
At the risk of derailing another user's thread, I thought from the title this would be about spring clips for holding TO-220 packages to a heatsink without screws. As it happens, I need to find some: what options do I have? Aavid?
Title: Re: TO-220 pin clips
Post by: raptor1956 on January 03, 2018, 07:50:04 am
Well, I guess I can remove them from the bread-board and solder to them -- that just makes the wiring mess even more of a mess.  Or, I could live with the less than elegant solution I'm now using with the mini-grippers connected with the MOSFETS in the bread-board.  I could, I suppose, solder to the pins and still plug them into the bread-board.

Title: Re: TO-220 pin clips
Post by: xani on January 03, 2018, 09:11:41 am
Just order a bunch of cheapo protoboards, they are below 0.5/piece and are nice for ad-hoc prototyping ( (
Title: Re: TO-220 pin clips
Post by: tooki on January 04, 2018, 03:53:15 am
Also, a trick that can be handy for TO-220 (and similar) devices on breadboards: use flat-jawed pliers to twist the pins 90 degrees, so they're flat, in parallel with the contact strips. This provides better contact, and doesn't bend the breadboard contacts out of shape.