Pigtail for TO-220 Package - Page 1
Forum section: electronics / general

author: t1d
author_rank: Super Contributor
timestamp: August 15, 2018, 11:02:01 pm
content: I am building a DC Electronic Load. I would like to use a pigtail, to wire the MOSFETs. That is to say, I want to be able to set all of the MOSFETs on the heat sink, secure them, with the HS bar clamp and just plug in the MOSFETs. This connector would have the wires come out of it, to solder to their supplies.In the past, I connected all the common MOSFET pin, with 12 gauge wire. This made a fragile framework assembly, that was a pain to build.I am having trouble finding this pigtail. Maybe one is not manufactured. Or, maybe I do not know the right terms, by which to search. "TO-220 pigtail" and "TO-220 wire connector" did not produce any relevant results.Any help finding this item would be appreciated.

author: ogden
author_rank: Super Contributor
timestamp: August 15, 2018, 11:21:18 pm
content: You can't find "TO220 pigtail" because it's bad ideaHigh current power transistor is last thing you would want to plug into socket.

author: t1d
author_rank: Super Contributor
timestamp: August 16, 2018, 01:13:16 am
content: That makes sense. Thank you.

author: james_s
author_rank: Super Contributor
timestamp: August 16, 2018, 01:55:37 am
content: I've seen people use screw terminal blocks and you can also use friction lock type connectors with the standard 0.1" pin spacing like the sort typically found on computer fans. Proper TO220 sockets must exist too, I've certainly dealt with plenty of TO3 sockets and they work ok within reasonable constraints.

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 16, 2018, 05:03:26 am
content: Could you mount the TO-220 packages to their own small PCB with either a header or flyleads to then plug into the main PCB?

author: capt bullshot
author_rank: Super Contributor
timestamp: August 16, 2018, 05:30:11 am
content: Quote from: t1d on August 15, 2018, 11:02:01 pmI've seen people using three-pin Molex (2.54mm pitch) connectors using for that. But in general, it's a bad idea as others said.

author: james_s
author_rank: Super Contributor
timestamp: August 16, 2018, 06:55:55 am
content: I don't know that it's such a terrible idea in this context. I DC load implies linear mode, so the current through each individual transistor is probably pretty low. A Molex (KK?) connector is good for several Amps so as long as the leads are not unusually thin I don't really see it being a big issue.

author: Wolfgang
author_rank: Super Contributor
timestamp: August 16, 2018, 09:36:19 am
content: Hi,its a bad idea, as the others have said. If the root cause for the need for sockets is that your MOSFETs blow out so often, get LINEAR MOSFETs and use either equalization resistors or better a separate gate driver for each one.

author: james_s
author_rank: Super Contributor
timestamp: August 16, 2018, 04:49:32 pm
content: There are other reasons, needing to mount them remotely, ease of assembly, even if you never intend to replace blown parts there are situations where a socket makes things easier. Having not seen the design I can't comment on whether this is one of those situations.

author: ogden
author_rank: Super Contributor
timestamp: August 17, 2018, 02:11:07 pm
content: Quote from: james_s on August 16, 2018, 04:49:32 pmYou introduce potential point of failure(s) in your device. In power transistor case it is (to say politely) reckless decision. Other name: overengineering.

author: james_s
author_rank: Super Contributor
timestamp: August 17, 2018, 04:08:12 pm
content: I disagree. It is a technique that has a place, it is not something that one uses often but that is not the same as saying it should never be done. I have ~40 year old gear with TO-220 transistors mounted in this way and I have never had a problem with that particular area. There's nothing reckless about using an unconventional technique, especially for a personal project. We are not talking high reliability avionics here.

author: coppercone2
author_rank: Super Contributor
timestamp: August 18, 2018, 11:26:32 pm
content: can you post pictures of to220 connectors?I have just seen them bolted to random parts of the chassis with wires soldered to the legs, which were put into I think screw terminals. If you put wires on each leg, and heat shrink the legs, goop it, and heat shrink it further, it could be a reliable thingy with horrible electromagnetic specifications. You can also probably use a shielded wire in this case. I would consider it more reliable then something that clipped on the leads which are designed to be soldered. I guess this is what you are already doing?