Flyback diode - - - NEEDED ? ? ? Or RECOMMENDED ? ? ?

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,243
I've only recently learned about snubber RC's. The two concerns would be what the proper values are AND if they can handle the current. Startup is approximately 36 amps. Full speed running is around 19 amps.

The more I think about this the more I'm realizing I'm going to need a heck of a power supply for those currents. I have a 40 amp battery charger / engine starter in the garage. It's not small. And running this from a car battery will require a big battery and time to recharge in-between usages.
 

killivolt

Joined Jan 10, 2010
800
I've only recently learned about snubber RC's. The two concerns would be what the proper values are AND if they can handle the current. Startup is approximately 36 amps. Full speed running is around 19 amps.

The more I think about this the more I'm realizing I'm going to need a heck of a power supply for those currents. I have a 40 amp battery charger / engine starter in the garage. It's not small. And running this from a car battery will require a big battery and time to recharge in-between usages.
I read through this Thread, I'm confused did I miss something? No, offense, but when did it change from a blower at 6amps to 19 running amps? If the blower came out of a BMW I would think it should run on a 12v battery, I get you need to charge the battery during run time, but I'm just not sure where your going with it?

kv
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,243
Going with SBR60A45CT Schottky Diode, 60A 45V LOW VF.

Was reading an older thread where people have been buying from E-Bay and Amazon and getting factory rejects sold by unscrupulous people. Went with Mouser. Little higher price, but at least I have confidence I'm getting a good part. With shipping I decided to get a few extra so I'd have them if ever in the future I tackle a similar project.

@killivolt: When I picked up the blower I was told it drew 6 amps by the kid at the scrap yard desk. Knowing as I do that kids often speak with authority but without accurate knowledge, I set out to discover the true draw. One giveaway was the 10 gauge stranded wire. YOU DON'T NEED 10 GAUGE FOR 6 AMPS! So after finally coming up with a reasonable test rig I determined my starting amperage is approximately 36 amps and running around 19 amps. IF I were to power it from a power supply - it would obviously need to be quite a large supply. I have a RadioShack 13.8V 19A supply but it's far from capable of pushing the blower. It repeatedly goes into overload protection (something remarkable for a RadioShack product) but it just doesn't manage running the motor. Even with a small 12 volt battery on it - the PS from RS is just BS. So it's more than likely I will end up powering this from a spare car battery I have. I will keep it charged so it doesn't sulfate away. But finding a 40 amp PS - like I mentioned, I have a HUGE battery charger that is also rated to jump start a small car. That has a 40 amp setting. But I've never tested it out to see.

Anyway, I think I have a handle on where I'm going with this. I hope if anyone sees a potential problem they'll point it out. Believe me - I don't think of people being offensive toward me just because I don't know something. I consider the "Dumbest" question is the one nobody wants to ask. And THAT is dumb.
 
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Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,243
@killivolt: I've been planning on using a blower to stoke a fire in a fire pit. A more complete burn with less smoke would be nicer. OR I might build a heat exchanger that goes in the fireplace and extracts heat while allowing the fireplace smoke to rise up the chimney. Haven't fully decided yet, but the outlet port of the blower is approximately the same as a 1 inch copper pipe. Shouldn't be hard to come up with a mating system to hook it to either a fixed heat exchanger or a flexible hose with a copper end for a fire pit. Time will tell. Heck - this project may sit on the shelf for a few years. I'm just now looking at another job assignment in Wisconsin.
 

killivolt

Joined Jan 10, 2010
800
Going with SBR60A45CT Schottky Diode, 60A 45V LOW VF.

Was reading an older thread where people have been buying from E-Bay and Amazon and getting factory rejects sold by unscrupulous people. Went with Mouser. Little higher price, but at least I have confidence I'm getting a good part. With shipping I decided to get a few extra so I'd have them if ever in the future I tackle a similar project.

@killivolt: When I picked up the blower I was told it drew 6 amps by the kid at the scrap yard desk. Knowing as I do that kids often speak with authority but without accurate knowledge, I set out to discover the true draw. One giveaway was the 10 gauge stranded wire. YOU DON'T NEED 10 GAUGE FOR 6 AMPS! So after finally coming up with a reasonable test rig I determined my starting amperage is approximately 36 amps and running around 19 amps. IF I were to power it from a power supply - it would obviously need to be quite a large supply. I have a RadioShack 13.8V 19A supply but it's far from capable of pushing the blower. It repeatedly goes into overload protection (something remarkable for a RadioShack product) but it just doesn't manage running the motor. Even with a small 12 volt battery on it - the PS from RS is just BS. So it's more than likely I will end up powering this from a spare car battery I have. I will keep it charged so it doesn't sulfate away. But finding a 40 amp PS - like I mentioned, I have a HUGE battery charger that is also rated to jump start a small car. That has a 40 amp setting. But I've never tested it out to see.

Anyway, I think I have a handle on where I'm going with this. I hope if anyone sees a potential problem they'll point it out. Believe me - I don't think of people being offensive toward me just because I don't know something. I consider the "Dumbest" question is the one nobody wants to ask. And THAT is dumb.
I questioned because it just seemed the amperage was a bit excessive, 10 gauge might be in play because of out of control amperage for what ever reason. I looked around on some forums and found 5 to 6 amps is the suggested operating amperage for a BMW Blower Motor. The kid might just be telling the truth, if the blower is drawing that much amperage go get your money back. Here is the site I pulled the info from, it might give you some ideas, while speaking directly about the type of blower itself.

Oh and BTW I'm the King of Dumb questions:p

https://groups.google.com/forum/#!topic/alt.home.repair/tsWU9Nh5prE[1-25]

Good Luck neighbor,

kv:)
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,243
@killivolt Thanks for the link. However, it seems they're talking about the interior ventilation blower. Since that is controlled by different speeds, the FSU (whatever that is) is what seems to be failing under the load. Those sorts of blowers ARE less powerful, and therefore, less current. The blower I have is for secondary air injection into the exhaust system of the engine. From its construction it appears to be a double compressor, and therefore develops enough pressure to push air into the exhaust stream to facilitate burn-off of unburnt gasses.

The link also spoke of how difficult it is to reach the blower, given that it is deeply buried in the dash. Not so with the secondary exhaust air pump. It was under the right headlight, easy to get to and easy to remove. It would seem the link you provided is to a different subject. Maybe that's what the kid behind the counter was thinking of when he said 6A.

[edit] P.S. I don't believe in dumb questions. It's only dumb when you question whether your question should be asked.
 

MisterBill2

Joined Jan 23, 2018
9,231
The supply to use to drive that motor is a medium quality switcher that is not low-noise nor excellent regulation. No sense spending more money just to spin a blower. AND, for the highest speed on an automotive AC blower, 30 amps is expected.At least in some 1986 /87 Ford products.
Also note that since it was an emissions system part, neither the effect on performance or mileage was considered.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,243
OK, not sure how we're getting off track with AC blowers. This is a Secondary Air Pump. It's for pumping fresh air into the exhaust. Here's a few pictures of the pump (not blower; if I used the word blower before it was an error).

1009.jpg 1010.jpg 1011.jpg 1012.jpg
 

MisterBill2

Joined Jan 23, 2018
9,231
OK, now it is obvious what the thing is. Back in the late 1970s they were belt driven and they were vane pumps and there was an available option for jeeps to have a manifold so it could pump up soft tires. That alone screams PUMP, not blower. So you will indeed find that this device can deliver a lot of pressure, no idea about the flow. And CA blower would stoke the fire better, but be a much bigger challenge to hook up. Pressure and flow work a lot like volts and amps, and wall-friction in ducts, tubes, and pipes works just like resistance. So you will find that this device can deliver a fair amount of pressure, totally not like a blower.
 
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